Logic Pro 9 Logic 9 Midi sync drifts in and out by 1 or 2 bpm


New Member
In Logic 9 I have Transmit Midi Clock enabled in the Midi Project Settings so that the arpeggiators in my external synths can play in time with Logic. I have a combination of hardware synths and softsynths which I use in standlalone mode on an external PC.

However, the clock appears top drift randomly, flicking from the songs tempo (for example 120bpm) to small increments above and below that (120.6, 119.4 etc). I was first alerted to this by variances in the way the arpgeggios were playing back and have confirmed it using a Midi monitoring program on the external PC.

I use an emagic Unitor 8 as a Midi interface and despite its age it is rock solid in every other regard. Note on/off, controller data etc is all relayed perfectly.

Anyone got any idea what might be causing the clock to drift?

Kind regards,
There is a known issue with timing drift if your buffer is set too small or too large. I would try experimenting with the buffer sizes and see how that affects playback.