As regards switching multiple tracks between Linear and Musical Timebase, I’m afraid I haven’t found any solution.
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As I wrote a few posts up about this very issue a few days ago:
+1
Remembering the old days when we (too late) discovered that there were needed a few bars in front of an already recorded track. We then turned the tape upside down, and played number reverse while recording a new click track where the drummer followed the original track, and let him continue after the start was passed (in reverse). Played forward again, we now had a click track to start up with.
These are -very- helpful suggestions.
Kinda weird to have to have a separate click that is independent of the MIDI, but hey… if it works?
I just have to -remember- this whole process. 
So much to remember, so little time.
CHEERS!
—JC
PS: I worked off part of my college fees 30 years ago copying parts. I can’t even remember how little I charged, but if anyone’s wondering why I’m going through all this crap instead of just doing a mockup and then having parts copies? Well… Let’s just say part copying has gotten more expensive than I recall. Plus, I have the now rare chance to have my stuff played… so I get to find out how many changes I need to make! It’s not like I write it once and then ‘C’est Fini!’ I think I’m currently on REV-5… Having a way to go back and forth between notation and mockup helps a LOT.
Congrats on getting your music played by others, JC! I have all kinds of requests for my music too! (Unfortunately for my music they are of the nature of “turn that off, would ya!!!” 
).
FWIW - my click in the pause isn’t independent of my MIDI because I put in a measure at the end of the pause at the “subsequent tempo”. Sounds like you don’t need that, but I do because I am doing overdubs in the pause that use (but don’t slavishly follow) the MIDI beats there (like drum fills, etc.). Though I have to say, I’m still not sure how to get a fill to sound right in a pause that is bracketed by two different tempos …
Every once in a while one hears of a 60 year old woman who manages to conceive and bear a child. It does happen. It may begin pleasantly enough, but it’s all down hill from there. And from start to finish basically every aspect of the process is almost more trouble than it’s worth. And after the birth? The thing turns out to have some horrible defect because the whole deal goes against the laws of nature.
That’s what doing any notated music is like these days… especially if yer not in school.
I know exactly what yer trying to do… I would love to have a way to be able to pause for a ‘free solo’ and then have a two clicks for nothing at the new tempo.
Which is why I think a ‘Timer Event’ would be so cool. I envision you could drag it onto the Ruler as a ‘bar’ with a parameter for ‘time’ in milliseconds. It would just look like any other ‘event’. BUT you’d get a count off click for tempo at the next bar. And if you hit the Pause button (or a footswitch) at any point during the Timer Event, the sequencer would just hang there until you hit Play again… and then count you into the next bar. If I had -that- I’d be set–not just for notation, but also for syncing live musicians to the MIDI. The conductor could just hit a footswitch during the fermata/caesura and the MIDI would follow -him- rather than what I’m used to—being a slave to the MIDI.
Thanks again for the help.
—JC