>Supposedly simple concepts like 'track BPM' just don't work reliably in the real world. Sure it does, you just have to give up on the idea of there only being

>Supposedly simple concepts like 'track BPM' just don't work reliably in the real world. Sure it does, you just have to give up on the idea of there only being a single value. A song could have multiple different BPM values, so in your database you'd just record a set (or a tuple in Python parlance). For subtle tempo shifts, you'd run the music through some kind of filter algorithm which would isolate sections with significantly different tempos, then for each section would find the average, then would make a set with those values and store it. The only place this would fall down is some weird music with constantly-changing tempo, where you'd end up with an average over the whole song.