[CWuestefeld]

I haven't done the test, since I'm at work, but not having any concrete evidence never stopped me from having an opinion.

It may be that their algorithm is good enough to find highly-periodic "pulses" that are candidates to be considered as a beat. However, believe it or not, the beat is really a matter of individual perception (although people agree in many/most cases).

To me, this is most obvious in music typical of the "power metal" genre. This music frequently is annotated as "double-time feel", and its drumming alone would tend to indicate a beat twice as fast as what would be indicated if you concentrate on the vocals and other instruments. Thus you've got an ambiguity.

Training it so that it can decide whether people tend to perceive the doubled beat or the slower one might be what they're after.

Also, it's common in progressive rock and progressive metal to have frequent changes in time signature. When the beat is changing, what do you say the beat is? They might also be looking for a way to make this choice.

Of course, the genres of music that you mentioned tend not to have those kinds of variations, so maybe I'm just blowing smoke.

[smackfu]

It would also be interesting to see if people can tell apart very close BPM difference. Like if you play a song that is 110 BPM and then one that is 120 BPM, and and someone can reliably say which is faster, then your actual beat measuring becomes a lot less important. You can just build off a bunch of known values and have everything else relative to that.