My experience looking through ads of bands looking for a vocalist:
Male singer: You must meet all of the following requirements to receive a reply, much less an actual audition:
1: Must be between the ages of 18 and 25
2: Must be tall and handsome with perfect teeth and hair
3: Must have a full time well paying job (but be available at all times) and willing to help cover expenses
4: Must have transportation and be willing to haul equipment and/or other band members around
5: Must have at least 5 years of verifiable pro level experience
6: Must have at least 3 albums of professionally recorded material and 10 full length live videos
7: Must have at least a 3 octave vocal range and be able to sing cleanly and scream and growl
8: Must be dedicated (aka willing to shoulder most of the expenses, do most of the writing, never have your own opinion etc)
Female singer: You must meet the following requirements to get the gig:
1: Must be female
2: Don't be not female
3: See requirements 1 & 2
Of course those ads are at least better than the ones where the band can't figure out what they're supposed to sound like.
"We're like a mix of the Delfonics, and Danzig, and Britney Spears, and Mayhem, and Mozart, and Bruno Mars, and Testament, and Dean Martin, and Bauhaus, and Seeed, and Willie Nelson, and Eat Your Makeup, and My Chemical Romance, and Etta James and Van Halen and N.W.A., but with a really original twist!"