When you’re working with loops in your favorite software DAW, you’ll probably need to know the tempo in BPM (beats per minute). Most commercial loop libraries provide you with this information, but let’s say you recorded a bit of music while your band was playing. The whole recording might not be all that great, but if there’s a full measure that’s a keeper, maybe you want loop it and use it to build upon. Some of the more sophisticated software will do the math for you, but let’s learn how to do it ourselves.
First, edit the loop so it’s exactly one measure long and that it sounds good when looped (no weird clicks or pops at the loop points) and make sure you truncate the unused portions of the audio. With your loop open in your preferred application – we’ll use BIAS Peak for this one – go to the Audio Info window (in Peak, that’s Option > Audio Info). You’ll see that the document length is 130823 samples. If you’re not sure where to find that information in your application, you probably didn’t read the manual, so this might be a good time to look it up.
Since our audio was recorded at 16-bit resolution at a sampling rate of 44.1kHz, we multiply the number of samples per second (44,100) by the number of seconds in a minute (60) and we get a total of 2,646,000. Since there are four beats in our measure, we multiply our total by four and we get 10,584,000. This gives us the data we need, because in our next step, we’re going to divide that grand total by the number of samples in our loop: 10,584,000 / 130823 = 80.9, which we’ll round off to 81.
Finally, if we want to use that loop as the starting point for a song in our favorite DAW application, we’ll create a new project in whatever key the original was in (let’s just say A minor) at a tempo of 81 bpm. And you thought your fifth grade teacher was nuts when she insisted you learn math. Okay, you probably used a calculator, but still, math is math!