My 'BPM' column doesn't populate

Add the info yourself.

iTunes does not do it.

if you use DJ software like Serato, which reads your itunes library, you can auto-analyse your tracks, BPM detection is among the features. When done with analysing your library (or a selection), the BPM info is added to the ID3 tags. The next time you play these songs in itunes, the bpm field will be updated to the values Serato wrote in the tag.

Depending on the music genre, auto-analysing software is not always accurate. Generally it's no problem with electronic dance music, but the more complex the rhytms are, the more chance the detected values will be incorrect. (triplets can be detected as one-quarter note values etc...)

Forgot to mention:

You can download the "Serato Scratch Live" software for free.

To use the software for DJ-ing you need the Rane-Serato hardware, which acts like a dongle, and allows you to use more than one deck (needed for DJ-ing, duh :-))

If the hardware is not attached, the sofware functions in track prepare mode. (one deck)

So even if you don't buy the hardware, you can still use the sofware to analyse your tracks, and detect BPM values. First you select a BPM range, then you select the tracks you want to analyse and hit the analyse button.

After analysing you will notice that a small percentage of the tracks has a wrong BPM value due to complex rhythms, or misleading off-beat sounds in the music. These you can correct manually by playing the song, and tapping along the rhythm with your mouse, after a few taps the BPM appears, hit enter and the correct value is inserted (if you tapped it correctly).

And then there's still some music by musicians who find it funny to change the tempo within a song, but that's another story :-)

good luck