How do I set up 2 TM backups? 1 for my MBP and 1 for iTunes.

[Star Nuts]

When I select two disks, it seems there's no way to individually modify each backup. I can exclude certain drives from backing up but it'll exclude it for both, right?

 

[Weaselboy]

When I select two disks, it seems there's no way to individually modify each backup. I can exclude certain drives from backing up but it'll exclude it for both, right?

That is correct. With Mountain Lion you can setup multiple backup destinations, but the settings will be the same for both.

 

[dusk007]

Just use some other software for the Music like Carbon Copy Cloner or something more primitive.
As you don't need any version but only a copy of each individual file that is the easy way to go. In case of hdd fail you simple copy the entire folder back.

If the backup is on some network drive you can also access the music without starting up the notebook.