The recorder built into iReal Pro captures one pass through one microphone. For overdubs, effects, or editing, let GarageBand do the recording and let iReal Pro supply the band.

 

Open the song, tap or click Share, choose Share Audio, and export the backing track as WAV for full quality or AAC for a smaller file. Save the file, then drop it onto a track in GarageBand and record yourself against it as often as you like.

 

Older versions of iReal Pro could play into GarageBand through Inter-App Audio or Audiobus. Neither is supported any more, so export the audio instead.

 

See Record yourself on the iReal Pro website.