# Common denominator bpm

I have a video of nature. I noticed that there are three repeating elements, one has 80.197844 bpm, the other 64.664 bpm and the other 67.4 bpm.

I want to compose music for it. To get started, how do I find a common denominator bpm value to create music that includes all the rhythms without sounding contradictory?

• I would suggest starting off by rounding, but that won't help much because 67 is prime. If I were in your shoes I would remember that the main title theme to The Terminator is based on a loop that is not actually a full measure long at any tempo or time signature that matches the music, and the composer just performed along with it without a click track. So I wouldn't even try to get a firm tempo or beat, I would just play along as best I can and feel my way through it. – Todd Wilcox Dec 3 '15 at 20:10
• The elements don't feel like they are working together. If I focus on one element, the other one goes out of tune naturally. Isn't there any mathematical way to bring everything under one roof even though 67 is a prime number? – Anders B. Dec 4 '15 at 2:31
• Not that I know of, but I only took one semester of group theory. – Todd Wilcox Dec 4 '15 at 2:42

You need to find the ratios between the numbers, and try to fit these to round-number approximations. The actual values are not important (let alone microsecond precision!)

• 64.7:80.2 is close to 4:5 ...Easy!
• 64.7:67.4 is close to 24:25 ... hmmm

I honestly doubt if you can make anything musical out of a 24:25 ratio (other than poco piu mosso); I would think that it could be very interesting to make something out of 4:5 relative frequencies. (I hope this helps; I don't 100% understand what you plan to do.)

Construct simple, rhythmic musical lines at those three speeds and play them together. Maybe interesting cross-modulation patterns will emerge. Steve Reich did a lot of this sort of thing.

But, if nothing interesting DOES emerge, try a different musical concept. Remember, Steve Reich had to make a living doing furniture removals for a long time :-)

Having done similar projects, it's probably easier to speed up or slow down the videos so that they fit the music.

• It is not, as all elements appear in the same video at the same time. – Anders B. Dec 3 '15 at 20:01