I have a fairly large music collection in MP3s, and I like my files to be sensibly named and tagged.

One of the tools I use to do that is a Perl script I wrote named retag-by-filename, which allows you to provide a regular expression with named captures (so requires Perl 5.10 or later), and uses that to retag a bunch of MP3 files.

An example of it in use:

[davidp@supernova:~]$ ls -1 /shared/music/Complete\ Albums/Oasis\ -\ The\ Masterplan/ | head -3
01 - Acquiesce - Oasis.mp3
02 - Underneath The Sky - Oasis.mp3
03 - Talk Tonight - Oasis.mp3

[davidp@supernova:~]$ ./retag-by-filename --dry-run \
  --pattern="(?<track> \d+) \s - \s (?<title> .+ ) \s - \s (?<artist> .+ ) \.mp3" \
  /shared/music/Complete\ Albums/Oasis\ -\ The\ Masterplan/*.mp3
[01] Acquiesce by Oasis ()
[02] Underneath The Sky by Oasis ()
[03] Talk Tonight by Oasis ()

The --dry-run option shows the details of each track, but doesn’t actually update the tags. The --pattern option supplies the regular expression to match against filenames; you’ll use named captures named track, title, artist and comment to capture the appropriate parts. (In the example above, there is no comment to match.)

Thanks to the awesome power afforded by using modules from CPAN (Music::Tag and Getopt::Lucid), the actual script is 37 lines of code.