Decoding MIDI data from audio dump

Question

Warning: This is not a generic "how do I make a .midi from a .wav"? question.

While browsing my filesystem, I uncovered an old Alesis HR-16 drum machine's dump in WAV format. The device has a function to store its memory to a generic audio tape in some kind of binary format, then read it back. So one time my computer was used instead of a tape recorder.

Is it possible to convert such a memory dump back to binary data (or even MIDI data)?

(Edit: I'm just curious if it's possible. It's not a "backups? what backups?" situation.)

Answer 1

It sounds possible, but sounds like it would involve a lot of investigation to figure out the formats involved and write your own conversion programs. I tried searching for information to see if anyone had already done this but couldn't find anything. Here are some ideas, though.

I couldn't find the Alesis HR-16's tape storage format documented online. But I'm guessing it uses two tones to encode data bits with some sort of self-clocking signal. If you have an audio editing program with a spectrum mode (Audacity, for example), you might load the wave file into it and use the spectrum mode to easily identify the tones and look for patterns.

Once the tones are decoded into bits, they probably won't be a Standard MIDI File, but some internal memory format used by the Alesis HR-16 to store its patterns or songs. I found an HR-16 Service Manual that documents the memory dump formats it uses with its MIDI memory dump functions. I'm guessing the bits encoded into the tape storage format would be the same or similar.

Answer 2

I have a strong feeling that what you are looking at is an actual sample dump, and what you want is a sysex dump of the system's patches/OS. Did you make the dump by recording audio from the HR-16 into your computer's soundcard? If so, then there is a good chance that there is no more "hidden" data there aside from what you hear, and unfortunately that won't get you actual MIDI patches back.