I managed to convert the audio files into raw binary data. I used a modified version of an old utility I wrote for another project and it worked quite well. I had to manually fix some of the audio files or they wouldn't convert as is. Especially the first 2 or 3 Picturemate tracks had some issues (see picture) that could cause them not to work at all on real hardware altough I don't have a compumate an I cannot test it myself.
The picturemate tracks holds 2052 bytes each, while the songmate ones are 1540 bytes. The first 4 bytes are some sort of header, so there are exactly 2kb and 1.5Kb respectively (the compumate has 2kb ram built-in). As you can see in the following picture, I I typed a few bytes from the first Picturmate track into the ram in the Stella debugger and the correct picture started to appear on the rendered screen.
I also used the raw data to generate new audio files that should be more reliable. If someone wants to try them on real hardware and report if they work, it would be appreciated.
Here are the files:
compumate_tape_binary_v1.zip 22.64KB 65 downloads
compumate_tapes_remastered_v1.zip 1.1MB 77 downloads