

Last.fm launches crowdsourcing experiment for tempo (BPM) detection - nervechannel
http://blog.last.fm/2011/05/12/slow-or-fast-please-lend-us-your-ears

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bravura
"We’ve built a very simple application on our labs website where you can
listen to music and help us _improve the state of the art_ in tempo
estimation."

No. We are giving you data that you use to improve _your_ tempo estimation
algorithm. If you wanted to improve the state of the art, you would _share_
the data you collect.

In particular, you note the MIREX competition (<http://www.music-
ir.org/mirex>) earlier in your post. Share your data with the MIREX
competition, and make it open for use by others, if you want to improve the
state of the art.

~~~
nervechannel
Don't worry, we _do_ intend to share the data publically once it's all in.

~~~
dododo
given that there is no stated end date to this experiment, when exactly will
you post the data? ("once it's all in" doesn't say anything).

will you post all of the data (in its original, unadulterated form) collected
for free, unrestricted download by anyone for any purpose, including competing
with last.fm?

intending to share, and actually making a public promise to do so, are quite
different things.

~~~
nervechannel
The exact details are out of my hands -- I'm just a tech guy -- but we're
active members of the music information retrieval community and always have
been.

No-one even knows if it's _possible_ to crowdsource good enough BPM data like
this yet, so even demonstrating that it's feasible would be progress :-)

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xcallemjudasx
I sampled enough of the songs to get about 500 points(20-30 minutes) and they
really need to increase the variety of samples. Most of the stuff was older
pop hits (50's pop), some country, 1 rock song (Disturbed - Ten thousand
fists), and a couple of old rap songs.

I'm used to listening to metal, industrial, hardstyle, house, etc. All my
answers are going to be biased towards slow because even though the song may
be at 120bpm it still feels slow to someone who normally listens to things
closer to the 150-200bpm range.

A better sample to test will produce better results.

~~~
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.

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smackfu
Even with the app it seems really hard to find the beat. It's really easy to
find the bass hit though, so I wouldn't be surprised if a lot of the tempos
are off by 1/2 or 1/4.

~~~
CWuestefeld
Yes, definitely. That's part of what I was getting at with my reply elsewhere
in this thread (<http://news.ycombinator.com/item?id=2540866> ). The
_perceived_ beat can actually be different depending on who is listening, and
what they're focusing on.

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ltamake
That's pretty nifty. Something to do when you're bored.

