[sdiy] Bunching of MIDI clock messages

Richie Burnett rburnett at richieburnett.co.uk
Thu Sep 12 23:19:11 CEST 2013


Hi Brian,

> ...For example, I hope that you're not  triggering all drum samples at the 
> beginning of the 1 ms audio  buffer. You'll get better timing if you use a 
> constant 1 ms latency  and schedule drum samples to trigger at precise 
> points in time, with  different sample offsets for the start of the 
> trigger within each  buffer. Similarly, just as you wouldn't move all drum 
> sample triggers  to the beginning of the 1 ms buffer...

Well, that's exactly what machines like Roland's TB-303, TR-606, TR-808 and 
TR-909 actually do.  Their tempo clock is a free-running analogue oscillator 
that is polled every 2 milliseconds by the CPU, and the instrument trigger 
pulses are then all generated simultaneously for the appropriate 
instruments.  Also many of the old analogue synths like the JX and Juno 
series also scan the keyboard and update everything at a control rate of 
500Hz or 1kHz.  So their note onsets and ends are snapped to the nearest 
millisecond too.  It might not be the best that is achieveable with current 
technology but it was common practice back then, and I'll bet many DSP 
synths using block based processing follow the same path now.  (I agree that 
variables like LFOs and envelopes should be interpolated during 1 
millisecond processing frames though.  That is essentially what happened in 
the old analogue synths with all those CV demultiplexers, followed by RC 
filters to smooth each CV over consecutive control updates.)

Best regards,

-Richie, 




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