The band is a 5 piece and the instrumentation is: 1) lead female vocals, 2) keyboards/sax/vocals, 3) keyboards/trombone, 4) bass/rapper, 5) drums.
The best bet to find good music is to check the Austin Chronicle music listings or Do512.com the week you arrive. The Moody Theatre at the W Hotel is one of the best venues in the country. If they have a band playing that you like, you should definitely check it out. The 360 Amphitheatre at the Circuit of The Americas is also a great venue.