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[Sauzee]

I've just analysed the same song (Pieces Of The Sky by Emmylou Harris ) twice as I have a duplicate of the file. MC reports BPM as 63 on 1 file and 124 on the other.  Both files were mp3's.

The faster BPM is clearly wrong but how does MC manage to come up with totally different readings from exactly the same song?

This isn't the first time I've found this.  

Audio analysis in theory sounds good, but in practise I've not really found much use for it (excluding replay gain).

I love the idea of choosing high BPM and high intensity tracks when I'm in the mood, but the files MC comes up with are a very mixed bunch of fast, mid and slow tempo songs.

I'd be interested in others' experience of audio analysis and how they use it.

[hit_ny]

I've just analysed the same song (Pieces Of The Sky by Emmylou Harris ) twice as I have a duplicate of the file. MC reports BPM as 63 on 1 file and 124 on the other.  Both files were mp3's

What you see here is harmonics, the 124 BPM measure is the first harmonic. i find this happening a few times, AA will either report the track at twice the BPM or half the BPM.

i usually AA albums before i listen to them and have BPMs displayed in PlayingNow when i listen. If BPMs are wrong i correct it manually (listen/tap for 15s seconds then multiply by 4). After a while you get used to the beat so u can spot a wrong BPM. If you listen to mix albums that tend to have a constant BPM, its easier to spot the odd track with a wrong BPM.

I find BPMs very useful along with genre for setting mood. Intensity less so.

Its not a perfect science, but it helps.

[Sauzee]

hit_ny

Thanks for the tips. I'll try them out. I didn't know you could edit the BPM value.  

What are harmonics?  Thinking about this I'm starting to wonder how one defines the beat.  Some music has rhythms all over the place - what do you go for?

[hit_ny]

What are harmonics?

Harmonics

Thinking about this I'm starting to wonder how one defines the beat.  Some music has rhythms all over the place - what do you go for?

This is a difficult question...i think it depends on ur experience with the particular genre of music. From my incomplete knowledge of music theory, a beat is what the singers/instruments keep time to.

So u need to listen for a clear repetitive beat when the music is playing. It's not simple with the profusion of drum-machines used to synthesize modern music, but as u get used to a certain genre, you start to identify the beat from the accompanying rhythms.

It might be helpful to create a smartlist group with multiples of BPMs say (BPM < 50), 80, 100, 120, (BPM > 140) etc.

then take a random sampling for  a few tracks in each BPM group (adjusting for similar genre) and see whether they sound similar in tempo, the ones that are too fast or too slow will need a BPM correction. This might seem like a lot of work, but once u clean up the incorrect BPMs, random play (with crossfade) on a certain range of BPMs will be better.