With inspiration and musical mentoring provided by Seth Sternberger of _8-Bit Weapon_, I’ve impemented a percussion sequencer/synthesizer for the Apple II.
It allows a user to create sequences as long as 255 patterns, where each pattern is one of a set of 16 musical measures. Within each of these patterns, any one of 8 percussive voices can be played at any 1/16th note boundary. In addition, the “pitch” for playing back the percussion sample can be specified, which is useful for pitched drums, like tom-toms.
Like RT.SYNTH (which Seth also offers as DMS Synthesizer) DMS Drummer uses the DAC522 5-bit 22kHz pulse-width-modulation wavetable synthesizer
engine, driven by a sequencer that runs in real time. DAC522 represents “silence” as pairs of 6 cycle pulses spaced 46 cycles apart, regardless of whatever the code is doing–which subroutine it’s calling or which branch path it’s taking. Executing “branchy” code while maintaining a constant stream of evenly spaced pulses is pretty tricky, but it must be done if the sequencer is to keep silent except for the desired sounds.
Seth is offering the full version on his website:
It is available for $15, but the demo version (downloadable both from my website and his) is free for you to play with! It is limited to 8 distinct programmable patterns and the Save function is disabled.
Listen to the sample song, created by Seth, on either of our websites to hear the realistic rhythm line that an 8-bit Apple II can produce! The melody and bass lines are being played on RT.SYNTH, so the only non-Apple II-produced sounds are the “explosions” (which could also have been played by SOUND.EDITOR on an Apple II!).