How to determine BPM by timestamps/events

Question

I'm currently taking part in a scoring competition where the task is to score the music for a product trailer.

As common in trailer music I now want to sync my music with the trailer almost frameperfect, however this might get complicated if I can't find an equal timing on which all of the "hit scenes" (where typically a big percussion hit is to be expected) fall. My goal is now to determine a BPM so that all these "hit scenes" are more or less (a difference of some milliseconds between music and video is no serious concern here) frameperfect in place with the beat, so I can reliably score the track.

At the moment I have the problem that there might be some of these scenes correctly alligned with "Bar":00:00 or "Bar":02:00 but I also need to get rid of scenes appearing at timings like "Bar":02:31 or something alike.

I already went through the full trailer and wrote down all the relevant scenes with their according timestamp in [seconds:milliseconds]. Has someone any idea on how to calculate a suitable BPM from this information or has anyone done some syncing of music to a trailer and has experience with this?

Answer 1

Well, it comes down to basic math.

If you have a gap between two events of T seconds, and you want to score so that there are B beats between those two events :

1 beat = T/B seconds

BPM = 60 / (T/B) = 60 B / T

for example : you have 6s between two events and you want 8 beats between them, then BPM = 60 x 8 / 6 = 80bpm.

But when you have a bunch of events happening at times which were never designed to be related to each other - it is not very likely that you will find one tempo that will keep all of those events at places on your score that make musical sense. This is where your ability to write to the action comes in.

My approach to this would be to take the 3, maybe 4, most important events and look for a musical setting that works for those - then just see where any other stuff happens to land and score in "hits" at those moments.

Choosing a higher tempo might make it easier (but maybe doesn't fit the musical mood you want). Also you can of course have tempo changes, or rubato sections, which can make it all a lot easier.

Answer 2

If it's a pop video, the music keeps a steady tempo (probably), and the video is cut to fit it. But when it's the other way round - you scoring to existing video - it's quite likely you won't be able to find one tempo that puts a beat on each hit.

But musical hits don't have to be on the beat. If you feel the action needs a rock groove behind it for a bit, syncopation is your best friend!

And beware of lining the music up with TOO many action hits. 'Mickey-Mousing' can get. (Though see some examples - constant tempi aren't necessary.)