Do film composers generally write standard tempo markings in the score (e.g. 120 bpm) even if this doesn't exactly add up to the write SMPTE cue? For example, a passage to get to the next cue might actually need to be at 122.87 bpm rather than 120. Do they write 120 in the score and record at this marking (which would be easier for the musicians as 120 is so standard) and leave it for the editor to sort out, or do they record at 122.87 and have this in the score, which I can only imagine would make recording a pain?
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You record it at 122.87 bpm! Why would that be a pain?
The music editor wouldn't be expected to sort it out, much less the editor!
If the cue started and ended at 120 and there were no tempo-changes, the music editor could, after it was recorded, speed it all up to 122.87, but obviously that would also shorten the music. S/he wouldn't want to mess with it unless something had gone horribly wrong!
While writing the music the composer will have worked out all the tempi for each cue - it's rarely one tempo throughout a cue - and all the subtle slowing down and speeding up that's needed, making sure any audio/visual hits coincide correctly. All these tempi are written into the 'tempo track' of the DAW.
The metronome markings in the score and parts should give a rough idea of the tempi, but the musicians don't need to know precise speeds! Where they see poco rit., the tempo track may have a hundred tempo-changes: 92.00 - 91.90 - 91.80 etc." They don't want to see all that! They just want to see poco rit. and see the conductor's beat, and hear the slowing-down click track. So the metronome-marking is nearly always going to be approximate. For example, Crotchet=92 then poco rit.
Conductors scribble any additional marks they need into the score.