I am completely new to Garageband having never seen it before today. Trying to record a track with a MIDI keyboard I was surprised to find that the software bass instruments are about a quarter tone out of tune on some keys. How can this be? The pianos and brass seem fine...and the basses are OK in other parts of the range. I can work around the problem with the pitch wheel but this is very clunky! Any suggestions?

Yes, I've noticed that occasionally a few of the individual multisamples (that together make up the full pitch range) in some of Logic's bass Instruments are very slightly out of tune (and of course those are the same Instruments in GarageBand). In Logic you can open up the EXS Instrument plug-in, go in and tune them up, and the re-save the corrected patch, but in GarageBand you can't open the Instrument plug-ins so there's no easy solution. - You could open the MIDI CC display in the MIDI Editor pane and program in static/changing pitch corrections w/PitchBend as needed - You could use a third-party Instrument for bass instead—with a third-part Instrument you could open the plug-in and tweak the sound, if necessary

Thanks Joe, that's really helpful. I thought it might be a setting I had accidentally changed, but clearly it's not!