Stephen,
As Fran says, if you don't sing, it's gonna' be difficult at best. Though there are some folks who cannot carry a tune in a five-gallon bucket, most everyone can be taught to sing. I suggest checking into vocal programs offered by your local commumity college. Most have them, they are very reasonable and by the end of a few monts of training, you'll be amazed at the results.
After taking the singing lessons, put together a top-notch promotional package, one that jumps out with great photos, a CD, song lits, and a bio. All of these are very important to prospective clients.
Send out a flyer or card with a half-price offer, one that will at least get you in the door for that first time in locations where you hope to perform in the future. Include a CD witth the card or flyer--it works.
Learn to interact with the audience. I've seen lots of great musicians that sit down at the piano or keyboard, begin playing and never say a word to the audience between songs. You want to acheive the same intimate relationship with your audience that you had when you were performing for friends and family--a relaxed atmosphere where everyone is enjoying the music and having fun.
Good Luck,
Gary
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Travlin' Easy