MIDI drift?

I've encountered a strange problem in my current project. I've been spending the last several weeks trying to manually line up drum tracks from two sources: One group is bounced audio from Stylus loops, and the other is captured Giga audio from a MIDI track in the project. Giga is on a separate computer.

The problem is that I can line up the kicks from both groups in one part of the song, but they will not be together at a different part of the song. I discovered from zooming in and scrolling forward that the Giga tracks actually drift behind as the song progresses, meaning it's impossible for them to be on time all the way through the song. The Stylus tracks are on the beat the entire way through.

I don't understand how this is possible, since the Giga audio was triggered through a MIDI connection, and the tempo came out of the same project as the Stylus audio. I tried switching the sync mode to Full Chase Lock, and also enabled "Send Midi Time Code", and neither change yielded different results.

So now I'm out of ideas. Does this have anything to do with the sync settings on the soundcards of the two computers? Currently, they are both on Internal, because I thought it was irrelevant to the MIDI-trigger process. I have the cables to sync either computer to the other via Word Clock or SPDIF; if this would help I'd appreciate some instructions.

What am I missing here?

Thanks.

you are using two different clocks for timing of digital audio

I have had a similar problem several times with outboard midi gear.

I've been triggering a Proteus 1000 from Sonar and recording the audio back into the project and have found that as the song goes on, the proteus part gets more and more out of time. This is only evident, however, after the recording has been finished (i.e. it sounds fine when being recorded).

I have no idea why this is and (having tested similar setups using different software) I haven't seen this behaviour when recording from external units anywhere else.