Use autotune on Garageband with your MacFirst, create a new track. Click on real instrumental track. Create. Record your voice. Listen to the recording. Go to view, hide track editor. Go to enhance tuning. You can bring it to max for the TPain effect or choose the enhance tuning setting that you want. If you choose limit key, the program will keep you in the same key as your vocal key. (That was determined by the software.) For vocal effects, record a new track. Choose real instrument track, no effect, details, vocal transformer, edit. You can choose a preset vocal such as chipmunk, cartoon falsetto or monster. Record. Switch vocal preset and listen.