The singer's stage audition, anymore, is usually the "best 16 bars"--meaning that someone who knows what they want will know well before the 16 bars are through if they art interested or not. I am sure you can tell within the first half minute of a CD whether you are interested or not.

Also, you could save a bit of time, and loose nothing, if you simply pulled the CD out if it had drum tracks and synths, since this isn't what your venue uses, and simply said, "sorry, no synths or drum machines in our venue." Generally, one assumes that, for performances, the audition tape reflects what you'll hear in concert, unless it is a commercial recording, in which case, the performer should tell you what the instrumentation is. You know this, of course--I am just saying that, when you know you're not interested, you've given a fair hearing. Nothing changes if you listen to more..