MIDI Clock Drifts

Enigma

Member
Hey, all.
I've noticed that the MIDI clock on my PBC will drift when set next to other independent metronomes or MIDI clocks even when I keep it on the same preset. For example, I send it through a Molten Voltage G-Quencer (effectively a sequencer), and my MIDI clock and sequence will drift from my drummer's MIDI clock (he is using a Roland SPD-SX). The same effect happens when I start the metronome app on my iPhone. If I send my MIDI clock to my Hologram Electronics Dream Sequence the same thing happens.

These effects differ from pedal to pedal. The G-Quencer seems to drift a lot faster than the Dream Sequence. And the G-Quencer will drift faster or slower depending on which sequence I am using (probably the shorter sequences drift faster than the longer ones).

Have any of you experienced this? I understand that if I change presets it will effect the MIDI clock because the PBC operating system can't push both at the same time without effecting the MIDI clock. But considering that I am staying on the same preset the whole time what can account for this? Is MIDI clock just a very unreliable timing source? Or is there a programming issue with the PBC? I noticed that if I set the BPM to 116.9 on the PBC when the actual tempo is 117 it will stay in time for a longer period, though it doesn't sound quite right still.
 
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MIDI clock isn't really designed to have multiple clocks running. You really need to have only one clock, and run everything off of it. Just like my microwave and oven clocks drift out of sync over time, I would expect that any two MIDI clocks will do the same.

What makes it worse is that every MIDI message sent has the possibility of throwing the clock off, as you mention in your post. And, there is no mechanism for corrections or resynchronizing in the MIDI clock protocol.
 
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