Need guidance. How best to sync 1 audio with 1 MIDI track?

I usually just work in all MIDI, or all audio, so I haven't encountered this before and would appreciate a tip.  If you could just tell me in general where I should be looking, I would appreciate it.
 
The project has one 44.1/16 audio track, recorded to a click track.  The playing is by pros who stay on the click.
 
The project has one MIDI track of orchestral background parts, running at the same tempo as the click.
 
But - after a minute or two, they get out of sync.
 
At present, I have to split the MIDI track and slide various parts around to match the audio.  There must be an easier way, isn't there?  Should I be looking at AudioSnap?  Preferences, Audio, Driver settings, Playback Timing Master?  The Project, Clock Source is Audio; is that right?
 
Many thanks.

Probably the easiest way is to use a series of Set Measure/Beat to Now steps on the audio portion and then import the MIDI on to the time grid you have set up using the Set to Now process.

There are a bunch of different ways to do this, most of which require some knowledge of a work around for something that seems to work funky.

You can Audio Snap the audio to the MIDI grid, but it works funky and it will be a lot more work dealing with multi tracks.

best regards,
mike

Mike is right - this process isn't as intuitive as it could be but it can be done with a bit of effort & time.

Don't rush it!