A few weeks ago one of the bands I'm in needed a background singer, and I was elected to the position.
I'm a very average singer at best, but I did sing in choir in high school, and I know how to do basic harmony. I told the bandleader as much, but he insisted I sing. I reluctantly agreed. What I didn't realize was how saying yes would change the entire way I approach being a sideman. Here's some of the stuff I'm learning:
1. It's all about the melody. You become painfully aware of overplaying when you're singing along with the melody line you're supposed to be supporting. Every riff, harmony and rhythm should support the lead vocals, and if it doesn't, it needs to go.
2. Less really is more. You don't always have to make your chords dense, two-handed monstrosities. Let your left hand hang off the piano, and see how much better your instrument blends with the rest of the band.
3. If you sing, you raise your chance of getting the gig. It's simple: if a bandleader has a choice between hiring a backup singer and an instrumentalist, or a backup singer/instrumentalist, it's not going to be a hard choice to make (there are exceptions, of course.)
The bottom line is that no matter your instrument, the more versatile you can be, the more likely you'll be to be working. Be great at a couple of things, but be sure to be decent at as many things as possible.
What's gotten you hired in the past? Leave a comment and tell me about it.