I never really thought about it but a drummer has 2 hands and 2 feet; that's 4 percussion instruments that can be struck at the same time.  But are they really?

I'm no drummer so the best place to start programming drum patterns was using a book of drum patterns. I chose to start with 200 Drum Patterns by Rene-Pierre Bardet and a chart of the standard MIDI note number for the percussion instruments.

MIDI Music System was loaded up and a drum pattern was entered. Two or three voices were used for each pattern - A, B, Break. Then three more MIDI VOICEs were needed to sequence the pattern.  I've avoided entering more until now.

Trying to understand a voice file data has forced a much deeper understanding of note duration and clock cycles.  Notes with the standard duration can be inputted as W, H, Q, E, S ect. or you can input a "^" followed by a 192, 96, 48, 24, 12 ect. clock cycles.

As it turns out the drums can be programmed with duration of 1 clock cycle. Play them with a fast tempo and the drum instruments will sound like they were struck at the same time. Of course, MIDI is serial so nothing is played at the same time.
 
"Fast enough" is a rather loose term. The clock cycle is constant for a given note duration. A quarter note is 48 clock cycles.  The tempo is used to to set the speed at which the music is played. This a clock cycle period can change from 0.03571 seconds per cycle at 35 beats per minuet to 0.00431 sec/cycle at 290 BPM.

Say you want to play a base and snare drum at the start of a 1/16 note. The base and snare are played for 1 cycle and a rest for 10 cycles. That's the 12 cycles required for a sixteenth note.

C2^1, D2^1, R^10      or      C2^1, D2^11.

I have put together a couple of drum solos. RNB1.MUS was without using the ^ duration settings. ROCK1.MUS and RANDB1.MUS were hand coded into MMS voice 51-53.  Voice 1 was then programmed with a series of jumps to the patterns.  Change up the tempo and hear for yourself when the delay between strikes becomes noticeable.

drumtest.atr

Now I have a method of programming drum patterns and an understanding of the MMS voice file format.  If the M: device works under Diamond GOS I can start automating the task of programming drum patterns.