I would like to understand if I can (especially with macbook pro laptop rather than desktop/pro) use autotune on a live performance. My son plays keyboard and would like to be able to do this performing at church and elsewhere. Also, can such a thing be done with multiple users at once? I.e. if my son and daughter were to sing a duet (or maybe 3-4 people) can they each be pitch corrected? I know nothing about audio software, etc on the mac. Thanks in advance to anyone kind enough to answer my query.