The BK-9 can also have up to 7 loops, triggered either from the top 7 keys, or the FC-7 f/s. They can either loop (in sync and key with the arranger) or be one shot recordings. It plays .MP3's, .WAV and .AIFF formats directly from the USB stick.

Still not quite sure I understand the intent of the OP, though. Are you seriously suggesting a band or OMB that plays everything themselves, but the lead singer is a recording? Best of luck getting an audience behind that!

Backing vocals is another issue, but no audience really wants to see either lip syncing or completely recorded lead vocals. Even karaoke, the performer 'sings' while the band is recorded. I've never seen an act where the opposite is the case!