Luddite, that's some really cool stuff. What did you use to make the music from the Apple II? Sounds like you used some sort of pattern sequencer. Great stuff, man.
WARNING: Long-winded geekery ahead.
When I first got into the Apple II (c. 2001) one of my first projects was to write a drum sequencer. Fortunately a fellow by the name of
Michael Mahon had already written a 5-bit / 11 KHz digital audio converter, so all I needed to write was the sequencer itself and the UI... but since I'm not a programmer (and many would say
not a musician), it turned out to be quite a task. The result was
TimeLord, which is available from my
website.
Since then I've been refining the concept and a year or so back I came up with the idea of mixing 2 samples together prior to playback. Originally I was planning to use this concept to improve TimeLord (and still intend to), but as the
RetroChallenge approached and I needed to focus on something, the idea of creating fully-realized music that could be played off a single floppy became a bit of an obsession.
Obviously there are some pretty severe restrictions to work within, so it was going to be an exercise in minimalism from the get-go. First off, the sequencer can only work with 16 samples at a time, and the available memory of the Apple II limits each sample to 1.5 KB, or slightly longer than 1/8 of a second. Secondly, a 140 KB floppy disk doesn't exactly hold huge amounts of data... in the end I settled for 64 distinct samples for a total of 96 KB.
I arbitrarily divided the 64 samples into 8 sets. The first being assorted percussion sounds and the remainder were simple waveforms in octaves (without sharps or flats). The sounds were generated with Sound Studio in OS X, but in hind-sight it would have been quite trivial (although much slower) to do it on the Apple II.
The sequencer is really quite simple... it reads a single 8-bit byte from memory and transforms it into two 4-bit values, so that $F8 would become $F and $8 which represent samples # 15 and 8. These two samples are then "averaged" together in memory and the resulting mixed sample is played back.
The real trick was how to compose music with such a limited palette. I tried a few minimalist techno pieces, but I found the results a bit contrived. At some point in time, I was examining the audio samples' wave forms in the Apple II monitor and noticed there were a lot of repeating patterns with small variations, such as one typically sees in musical notation. I decided to feed some of these patterns into the sequencer and was pleasantly surprised by the result, so I decided to forego the composing stage and instead simply select interesting data from the audio stream. This had the added benefit of saving enough disk space to include a hi-res splash screen ;-)
The recording I posted was made with my Bell & Howell ][+ as it is by far the best sounding Apple II in my collection and the A/V "backpack" provides a convenient audio output. One thing that didn't make the recording is the 30-odd seconds of disk grinding that precedes each track... only on a genuine Apple II will you get the full multimedia experience ;-)
Anyway, that's the story... I'll bet you're sorry you asked. ;-)
