If you’ve downloaded music for a Disklavier Mark III or older model with a floppy drive, you might have downloaded a PSX file. If you have one of these files, hopefully this article can help you out!
What Is a PSX File?
For Yamaha MusicSoft, a PSX file is an archive format that contains the music files, much like a ZIP or RAR file. However, the only way to extract these files is by using the MusicSoft Downloader, which isn’t easy to find because the link on the MusicSoft website is broken or missing. Here’s exactly what I did to make it work:
Step-by-Step Guide to using PSX Files
Step 1: Download Your Music File
First, make sure you’ve already purchased the album or song from Yamaha MusicSoft. If you haven’t yet, log in to your account on their website, go to “My Account,” find your purchases, and download the PSX file to your computer.
When you install the MusicSoft Downloader, it might look like nothing happened—there won’t be any shortcuts or icons added. Instead, the program associates itself with PSX files. You’ll notice your PSX files now have a new icon that looks like a key. That’s the only way you’ll know it’s installed.
Step 4: Transfer the PSX File to a Floppy Disk
Double-click on the PSX file you want to use. The MusicSoft Downloader will open.
It will prompt you to format a floppy diskette and extract the PSX contents to it. Make sure you check the type of diskette (2DD or 2HD) before clicking OK.
The program will create an ESEQ formatted floppy disk with ESEQ music files. Once the process is complete, the disk will be ready to use with your Disklavier.
Step 5: Copy the files using PPFBU
Follow the instructions on my Floppy Disk backup page to store the actual files on your computer. These can now be prepared for use with a Nalbantov or another emulator.
Step 6: Play the Music on Your Disklavier
Insert the floppy disk into your Disklavier’s floppy drive, or the USB stick if you did step 5, and you should be able to play the songs directly from it.
One of my favorite simple upgrades for early Disklaviers is connecting them to PianoStream! PianoStream is a piano radio app designed to work with nearly every player piano, including the Yamaha Disklavier.
The app offers its own version of piano radio, providing you with a very large repertoire of high-quality music. It also allows you to stream MIDI files from your phone to your Disklavier, altogether bypassing the floppy drive.
Many customers choose to upgrade their old floppy disk drives with a Nalbantov floppy disk emulator. These devices altogether replace the original floppy disk drives. You can then store your entire inventory of floppy disks on a single USB stick!
At this time, if you want to record with your Disklavier, the Nalbantov is a necessary upgrade. The PianoStream App does not currently support recording.
Replacement Power Supplies
Power supplies on this generation of Disklavier almost invariably fail. Fortunately, TAP Electronics rebuilds Disklavier power supplies. Simply ship them your power supply, and they’ll rebuild it and ship it back. They remain the only provider endorsed by Yamaha for this service. Last I checked, this was a flat rate of $750. The rebuilt power supplies do not have the defect the original did, and will last much longer.
The Yamaha DKC-850 can be installed as a “piggybacked” device on the earlier Disklaviers. This means that the DKC-850 is installed in addition to the original Disklavier, and connected through its MIDI jacks. This adds most features of modern Disklaviers, including Yamaha Piano Radio and conventional USB ports.
The most common question I get about Mark IV Disklaviers is how to connect them to the internet. Oftentimes, the owner is struggling to connect, even though they know their device is plugged directly in to a live internet connection. In that case, you need to update your Mark IV firmware. Out-of-date firmware will not talk properly to Yamaha servers! If you have any trouble updating on your own, you can order my firmware update kit.
DKC-900 Upgrade
The Mark IV can be upgraded with the Yamaha DKC-900. This enables you to use your phone or tablet to control the piano, and is aesthetically much subtler than the Mark IV.
Nalbantov Floppy Disk Emulator
Has your floppy disk drive stopped working? If you want to gain back that functionality, you can install a Nalbantov. On the Mark IV, this is much less useful than on previous Disklaviers, as most of your disks are already saved on the hard disk.
PianoStream
The PianoStream App does also work on the Mark IV. This is an alternative to Yamaha piano radio, and is less expensive. It also allows you to broadcast MIDI files to the piano from your phone or another device. Of course, with the Mark IV, you can already use USB sticks, so this isn’t as large an upgrade as it is on previous Disklaviers.
Solid State Hard Drives
Sometimes hard drives fail on the Mark IV. The Mark IV uses old spinning disk hard disks. If you notice them chattering or exceptionally slow performance, consider upgrading your Mark IV to use an SSD.
The Enspire and the DKC-900 represent major upgrades over previous generations of Disklavier; however, they are still surprisingly challenging to connect to the internet. See my article on a straightforward and effective way to connect your Disklavier to the internet.
I use a wide variety of software tools when reading floppy disks and preparing ESEQ and MIDI for the Yamaha Disklavier. Below is my attempt to compile the most useful tools I use on a daily basis. If you have any input or want any further information, please don’t hesitate to contact me.
A comprehensive disk-imaging suite for Windows. Notably, it successfully transfers Yamaha Electone Performance floppy disks when other tools see them as unformatted. Although it can read some Clavinova and Electone floppy disks, it can not read Disklavier floppy disks. Nonetheless, it’s a versatile floppy disk tool, and a worthwhile addition to your arsenal.
ESEQ Explorer Facilitates the creation and management of PIANODIR.FIL for Yamaha Disklavier. Using ESEQ Explorer, you can create PIANODIR.FIL directories for your ESEQ files. This is necessary for older Disklaviers, and also allows you to modify song titles and metadata.
MIDI2SEQ Convert standard MIDI files to ESEQ for early Yamaha Disklavier compatibility.
ESEQ2MID Transform Yamaha Disklavier ESEQ files into standard MIDI format. This tool is extremely helpful if you’re transferring your songs from floppy disks from an older Disklavier, to a USB stick for a newer one!
MID2PianoCD is a Windows utility by Mark Fontana for encoding MIDI and ESEQ files into player piano-compatible formats. It supports various electronic player piano systems, including Yamaha Disklavier, PianoDisc iQ, Live Performance LX, Marantz Pianocorder, and QRS Pianomation. You can use it to generates CDs that can be played directly on MIDI player pianos, expanding the versatility of your Disklavier’s music library.
Mark Fontana is an extremely knowledgeable and talented individual, and his software — both this and PPFBU below — are vital staples. He requests donations on his website, and if you find his tools useful, you should support him.
Player Piano Floppy Backup Utility (PPFBU) is the premier Windows-based tool for backing up Yamaha Disklavier and PianoDisc floppy disks. It’s an indispensable tool for backing up your old floppy disks. He requests donations on his website, and if you find his tools useful, you should support him. It has a user-friendly interface, and can be used with USB floppy disk drives, even when Windows cannot see or open the disk.
Giebler produced a utility with wide-ranging compatibility with Yamaha devices. It will read older Yamaha Clavinova disks, in addition to Disklavier disks. However, this software is old, requiring versions of Windows that mostly can’t even be installed outside virtual machines. If you’re interested in how to get this running, read my article on using Giebler to explore old Clavinova disks.
For nearly all purposes, I recommend PPFBU above, although in isolated circumstances this software might make more sense for your particular project. Yamaha still recommends them today.
All software runs under MS-DOS on IBM PC-XT, PC-AT, or compatibles with a hard disk drive and an internal (non-USB) 3 1/2” floppy disk drive. Most programs are also compatible with MS-DOS shells under Windows 3.1, 95, 98, or ME.
The Greaseweazle allows you to duplicate your Yamaha Disklavier floppy disks — or any other floppy disk — without Windows even necessarily being able to open it. Even better, the Greaseweazle can read your floppy disk as an .hfe file, which you can simply drop onto your Nalbantov USB emulator! It can be used in place of all the tools mentioned above.
The Greaseweazle captures raw flux transitions from drives, enabling the capture and analysis of any disk format, including those used by Disklaviers.
FlashFloppy is a powerful firmware solution for Yamaha Disklavier floppy drive replacement and management. A Gotek floppy disk emulator with FlashFloppy installed, used in conjunction with the Greaseweazle, is the single most reliable method of reading floppy disks in USB stick format.
When paired with Greaseweazle, a Gotek with FlashFloppy becomes an exceptionally powerful tool for managing Yamaha Disklavier floppy disks. Greaseweazle captures raw flux transitions to create accurate disk images, which can then be easily written to or read from using FlashFloppy on your Disklavier.
FlashFloppy is open-source, and Keirf’s tools are incredibly valuable for our purposes transferring old floppies. The FlashFloppy firmware can be challenging to install on a Gotek for the first time, so purchase a Gotek with FlashFloppy already installed.
The alternative to FlashFloppy is HxC’s custom firmware which is paid/closed-source, but is used by Nalbantov below:
Nalbantov provides premium floppy disk emulators tailored for specific Yamaha Disklavier pianos, offering seamless integration and exceptional compatibility. The Nalbantov drive comes with guaranteed compatibility and is easy to use, and their support is excellent.
The Gotek and FlashFloppy solution described above will work as an inexpensive alternative; however, it can be a challenging DIY project, and is not advisable for anyone who isn’t quite comfortable tinkering with their own hardware. Additionally, Nalbantov manufactures slimmer drives that fit in models of Disklavier the Gotek does not.
They support a wide range of Yamaha Disklavier models, including early models (MX22, MX80, MX85, MX100A/B, MX116) and advanced models (MX500, Mark II/IIXG/III), as well as various Disklavier Control Units (DKC50R, DKW10, PPC3R, etc.).
For Disklavier owners seeking a reliable and easy-to-use floppy disk emulator with guaranteed compatibility across numerous models, Nalbantov is the best choice. You can search for your model of instrument on their website, and they will send you a properly configured device accompanied by a compatible USB-stick.
GNMIDI is a powerful tool designed for musicians, educators, and MIDI enthusiasts to play, edit, and convert MIDI files with ease. It’s very useful for converting MIDI files from Type 1 to Type 0. You’ll need this tool to prepare MIDI files you find on the internet for your Disklavier. The professional version allows you to perform large, batch operations, but the lite version works to convert files individually.
I was recently contacted by a person attempting to copy their Yamaha Electone Performance Disks. These files are not visible on Windows, and if you attempt to open the drive you’ll see “The disk in Drive A is not formatted.” This is typical of Yamaha’s proprietary ESEQ format, and does not necessarily mean there’s anything wrong with the floppy disk at all.
Copying the Files
None of the tools I typically use for reading Yamaha Disklavier floppy disks worked with the Yamaha Electone disk. However, I was able to easily open them with WinImage (https://www.winimage.com/). This was exciting! Give this piece of software a try, and see if you’re able to copy the contents off of the disks directly.
This will allow you to write them to another floppy disk, or store the files for the future. The software is shareware, and costs $30 after 30 days; however, this will give you plenty of time to verify that it works for your disk duplication needs!
Imaging the Disks (with optional Greaseweazle)
You can also save these images as .ima files, and they should be suitable to convert to .hfe files for use on USB floppy disk emulators such as the Gotek or Nalbantov. This is an option even if you cannot read the floppy disks at all.
The files on the Yamaha Electone performance disks do not easily convert from Yamaha’s ESEQ format to MIDI. The files on these disks appear to be .b00 and .evt files. The .b00 files are consistently sized at 14,336 KB, and there’s one for each .evt file.
Yamaha service note from 2004 refers to Giebler’s Yamaha DOM package, which is used for copying Clavinova and Disklavier files. I’m in the process of transferring files in a Yamaha CLP-156, a Clavinova from 1994, which uses an early version of ESEQ. I was curious to see if Giebler’s software package gave me better results than the more modern tools I have available, and if it might have an edge reading older disks.
You can view the Yamaha DOM Package from Gary Giebler on the Giebler website. It’s a bit pricey — $54.95 at the time of this writing. But it’s a specialized tool!
However, it requires an MS-DOS based version of Windows. I couldn’t get it to run in FreeDOS, as it required a Windows environment for the installation. However, I was able to get it running on Windows ME, running on physical hardware with an internal floppy disk drive. This is a very high bar to clear for installation — Windows ME and Windows 98SE are hard to install on modern hardware, to say the least, and Windows ME barely ran on the 2008 era computer I used for this process. So I looked for a better solution.
Running Giebler’s Yamaha DOM Package on a VM
Eventually, I was able to improve on this. I’m now running it on a virtual machine using VirtualBox. To start with, I had to install Windows ME, and found a Windows ME VDI ready to use on Internet Archive. The Giebler software will install only in the Windows environment, but on the virtual machine it won’t run in it. It was necessary to install DOS Mode for Windows Millennium Edition, and then reboot into DOS. Obviously it can’t directly read the floppy disk drive from within VirtualBox, so I make images of the floppy disks, and then attach those to the session after booting into DOS.
If you’re interested in making floppy disk images for use with Giebler’s Yamaha DOM package in a virtual machine, you’ll find a Greaseweazle is just the tool to make high-quality images of your disks.
Reading a Yamaha Disklavier Floppy Disk
Finally, I got everything installed, and I got to the first screen. This software has the following options, and none are particularly helpful for our purposes:
The Yamaha Disk Manager control screen. (Serial number and name are scrubbed from the status bar.)
I tried a handful of disks with it. I found its performance at reading disks somewhat limited compared to modern tools like Mark Fontana’s Player Piano Floppy Backup Utility (PPFBU). But it was able to look at disks and list their contents, and it had a pleasant old-timey feel. See, for instance, a directory listing:
The directory listing for a Christmas album I used as a sample.
I attempted to make a copy of the disk, and was met with an error. “Illegal to Copy!” As you can see in the above screenshot, Giebler’s Yamaha DOM package notices that the disk is “Copy Protected!” And it alters its behavior accordingly.
Reading my Clavinova Disk
So now, for my Clavinova. First, using Yamaha Disk Manager (YDM), I copy the track to the local disk:
Copying an MDA / ESEQ file to the local disk.
And then, I open up the DOMSMF application. At this point, I can select “Convert Yamaha to Midi” and, remarkably, it works!
Instructing DOMSMF to convert the MDA file to MIDI.Playing the song in Windows ME (before transferring it to an actual computer from the modern era)!
Note that tempo and track data are successfully transferred. This information is lost by DKVUTILS when converting MDA files to MIDI.
Yamaha’s earlier floppy disks use the propriety ESEQ format. They also use a primitive form of copy protection, where the first sectors of the disks are missing. This means computers identify the disks as corrupt, requiring you to use specialized software to back up your Disklavier disks. In place of these sectors, Yamaha uses the PIANODIR.FIL file, which serves both as a file table and a song index.
PIANODIR.FIL files are not necessary for MIDI files. Do not generate a PIANODIR.FIL for your MIDI files. It will make the disk unreadable to the Disklavier. The PIANODIR.FIL is only for ESEQ (or .FIL) files.
Please also note that, if you’re using the Pianostream, you do NOT need to convert your ESEQ files to MIDI, or do anything with a PIANODIR.FIL. The Pianostream will allow you to play MIDI files to your Disklavier without doing any of this. This article only applies if you’re using floppy disks or floppy disk emulators.
MIDI files that have only one track are called Type 0 files. MIDI files with multiple parts are Type 1. Occasionally, the piano will be spread between two tracks. In that case, you’ll find the piano is playing only half or so of the notes it should be. You can convert Type 1 to Type 0 files using the tool GN MIDI Professional. In addition to converting files individually, the professional version can convert batch groups of files. It has a 14-day free trial, and will either run on Windows or on Linux/Mac using Wine.
Once you download DKVUTILS.ZIP from my site or theirs, you’ll need to extract it. The program that converts MIDI files to ESEQ files is MID2ESEQ.EXE. This program runs only on Windows, and does not seem to run with emulators. Reach out to me and I can assist with conversion.
Using MID2ESEQ, just drag and drop MIDI files into the window.
If you have a Yamaha that’s capable of playing ESEQ only, you might also need to create a PIANODIR.FIL index. Continue scrolling down for instructions!
Creating a PIANODIR.FIL using ESEQ Explorer
If you are creating a floppy disk for use with an earlier ESEQ only Disklavier, or if you’re preparing ESEQ files for transfer to a Nalbantov USB stick, you might have to create your own PIANODIR.FIL.
Note: Please note that the filenames should be strictly eight characters long, have no spaces, and be entirely uppercase, including the FIL extension BEFORE following the process below. If you don’t do this, some pianos will be unable to read the files. I’ve created a program to conveniently rename all your .fil files at once, which is especially helpful if you have numerous albums.
First, put all the ESEQ files you’ve created in a folder together. The DKVUTILS suite includes a program called ESEQ Explorer. Once you open the program, select the directory you’ve stored your ESEQ files in (make sure they’re properly renamed according to the above instructions, or use my program to rename them for you). You’ll see a screen like the one below:
ESEQ Explorer displaying the contents of a Christmas album, with a proper PIANODIR.FIL file already in place.
Note that, if you don’t currently have a PIANODIR.FIL, there will be a red X in front of it. That means it’s not present. Right-click on it and select Create Index. The contents of that folder are now ready to be added to a disk using the Nalbantov tools. If your file names are too long, you’ll see them renamed with ~ symbols. In my experience, this is a program, and indicates they likely won’t read in the piano. Make sure to rename them appropriately first.
I’ve also quoted the text file from the DKVUTILS.ZIP tool below, since they’re informative:
Yamaha Disklavier discs are always on Double Density (2DD) media, High Density (HD)discs, which are more common nowadays, will not work. Furthermore, they are formatted to 720 Kbytes not the default of 1.2 Mbytes. The original discs are copy protected. This has been achieved by placing invalid data on the first sector. As DOS and Windows always refer to this sector to check out a floppy, they will report that the discs are bad. The Yamaha machinery ignores the first sector, so it reads them normally.
The music files on a Disklavier disc have the extension .FIL. They are frequently identified with titles like PIANO001.FIL, but sometimes they have names similar to DOS like MUSIC1.FIL. In addition to the music files, there is an index file on the disc. This contains a list of the active music files on the disc, their titles, and pointers to their position on the disc. The index file is always called PIANODIR.FIL and always has a size of 6 Kbytes. In order to set up a Disklavier disc to function on a Disklavier, you must first copy the music files onto it in Disklavier format (ESEQ) and then run the ESEQ EXPLORER program to build the index file.
Finding More MIDI Files
If you’re having fun converting these files, and you’re looking for more MIDI files to convert for your Yamaha Disklavier, check out my directory of MIDI resources!
This post is intended to help you read from, write to, or replace Yamaha Disklavier floppy disks.
Some of my customers choose to upgrade their older Disklavier’s floppy drive to a Nalbantov USB drive, and want to know how to copy songs from their old Disklavier floppy disks onto a USB. Some of them just want to be able to back up their disks in case they need to make new ones later. Or maybe, you’re just trying to figure out how to write to disks your Disklavier can actually read!
If you’re adding new music to a floppy disk or Nalbantov USB and have an older Disklavier (such as the popular MX100II), you’ll need to make sure the files are in Yamaha’s proprietary ESEQ format. Using the tools below, you can convert your MIDI files to ESEQ so that they will be in your Disklavier’s native language.
The content on the original floppy disk is protected by copyright and is the property of its respective owners. These instructions are provided to assist owners of legitimate copies in converting the files for personal use on their own Yamaha instruments. Unauthorized copying, sharing, distribution, or commercial use of the converted files is strictly prohibited. By using these instructions, you agree to comply with all applicable copyright laws, licensing agreements, and Yamaha’s terms of use. I disclaim any responsibility for misuse of the information provided. Do not ask me for free copies of Yamaha floppy disk images. I will not provide them.
Yamaha floppy disks are a great source of songs that you know will be formatted correctly for your piano. However, floppy disks often don’t age well, and are very susceptible to sunlight and magnetic fields. (This is one more reason to back them up!)
Disklavier floppy disks cannot be natively read by your computer without special software. They will appear as unformatted disks.
There are several tools that will allow you to read them: I use the Player Piano Floppy Backup Utility 1.4, created by Mark Fontana. It’s freeware, but he requests donations. You can download it from him, or you can download ppfbu_v1.4_setup.exe from me. It can read and save directly in ESEQ format, even if the disk it’s reading from is in MIDI. It appears to run acceptably on Mac / Linux using emulators, although this can add complications. When backing up Disklavier floppy disks, there’s no other single tool more useful than PPFBU.
If you copied the files in ESEQ format, there’s an extra step before your Disklavier can read them. See below!
The Player Piano Floppy Backup Utility v1.4 running on my dedicated “floppy copy” box.
Obtaining even More ESEQ Files from the Internet
In addition to the originals you might have, you can sometimes find these on eBay or at local music stores. Older disks on eBay are seldom tested, so there’s some risk of receiving junk disks.
There are several large online repositories in both ESEQ and MIDI formats. Some of these are of dubious legality. One legitimate resource was kuhmann.com, which had quite a large repository. I have a copy of their entire database. (I worry a lot about these older resources disappearing! They disappeared. Kuhmann’s inventory does appear to be available on the Wayback Machine, but his original website is now off the internet.)
You can also source files from Yamaha’s website, although this a more expensive option. Many of their MIDI files have multiple instruments (or even limited piano), and are more designed for their keyboards and other MIDI devices. However, they do have an entire category of Piano Solos, and these are what you’ll want to search for when selecting files. When you download these, you get their associated MIDI files, which are comfortably sized for floppy disk purposes.
Converting MIDI files to ESEQ
If you want to use MIDI files with your older Disklavier, you can, but you have to convert them to ESEQ first. Yamaha Disklavier floppy disks of the era all used this proprietary format, and these Disklaviers cannot read MIDI files natively. However, there’s software that does this conversion for you. You can either get it from http://www.carolrpt.com/MIDItools.htm or you can download the whole DKVUTILS suite from me.
Once you download DKVUTILS.ZIP from my site or theirs, you’ll need to extract it. The program that converts MIDI files to ESEQ files is MID2ESEQ.EXE. This program runs only on Windows, and does not seem to run with emulators. Reach out to me and I can assist with conversion.
Using MID2ESEQ, just drag and drop MIDI files into the window.
MIDI files that have only one track are called Type 0 files. MIDI files with multiple parts are Type 1. Occasionally, the piano will be spread between two tracks. In that case, you’ll find the piano is playing only half or so of the notes it should be. You can convert Type 1 to Type 0 files using the tool GN MIDI Professional. In addition to converting files individually, the professional version can convert batch groups of files. It has a 14-day free trial, and will either run on Windows or on Linux/Mac using Wine.
Using conversion software to merge all the MIDI tracks.
Please also note that the ESEQ filenames should be strictly eight characters long, have no spaces, and be entirely uppercase, including the FIL extension BEFORE creating the PIANODIR.FIL file. I’ve created a script to automate this proper naming process, discussed in my creating a PIANODIR.FIL index instructions.
Formatting 2DD Floppy Disks
Some people choose to use the original floppy disk drives in their 90s-vintage Disklaviers, rather than converting to a Nalbantov. First, it’s important to make certain you’re using the correct floppy disks. The more “modern” 2HD floppy disks require stronger magnetic fields to write, and may not always be compatible with older Disklaviers. The slightly older 2DD drives, however, will work. You can tell the difference readily: 2HD disks have openings at both corners of the Disk, while 2DD disks will have only one.
2HD disks have openings at both corners, but 2DD disks do not. You’ll usually find the write-protect slider in one corner, but the other will be blank.
Some have reported covering the hole with electrical tape will trick the Disklavier into believing the disk is a 2DD disk. You may or may not be able to write to it using the Disklavier, but you should be able to read from it using this trick, provided your 2HD disk is formatted as a 2DD disk.
Formatting a 2DD 720KB floppy disk in Linux.
I formatted mine on my Pop!_OS Linux machine with the instruction sudo ufiformat -f 720 -v /dev/[yourdevice]. If you’re using a Windows machine, the instruction is format a: /t:80 /n:9. Pictured below, you can see what this command looks like on my Windows XP floppy transfer box. This command does work in Windows 10 and 11, but requires you to be using an external floppy disk drive that allows this format. Not all of them do.
Formatting a 720 KB 2DD floppy disk in Windows XP.
At this point, you can transfer your .FIL files and PIANODIR.FIL file to your floppy disk. Put them in the root directory, and do not use any folders.
If you’re using an actual floppy disk, it must be a 2DD disk formatted to 720 KB. See the above section on identifying the disk and formatting it correctly.
You cannot have both ESEQ files and MIDI files on a disk, even if your particular Disklavier can read both file formats. Each disk or virtual disk must use only ESEQ or MIDI.
Earlier Disklaviers can be finicky about their ESEQ files. Sometimes, they’ll work without any trouble, even without a PIANODIR.FIL file. However, particularly in earlier Disklaviers (such as the DK5R), you’ll need to be more careful with the naming conventions, and you’ll definitely need that PIANODIR.FIL described above.
I’m very grateful for the research of Mike Isreal (in the comments below), who did experimentation with his own Disklavier. Beforecreating a PIANODIR.FIL for your disk, make certain that all filenames are precisely eight characters long, and that both the filename and extension are in all-caps. The filename must contain no spaces.
Some have commented that it appears you can also omit the .FIL extension (at least in some cases). According to Nalbantov, there might be cases where a fully lower-case filename and extension are called for, although I have not run into that particular case yet.
