There are three main types of songs in the SCA: period songs, modern songs written in period styles and filk songs. Talent in singing (although much appreciated) is not essential for you to be able to take part or perform.
There are many resources available on the Internet whether you are just starting out in your bardic studies or if you are an old hand at it. If you're experienced please take the time to teach a new person a song or six, or even teach a class about it!
Here's a good starting point: Celtic Cadence's Bardic Hall. It is a growing online repository/Bardic College where you'll be able to find an immense amount of information on the various bardic arts (not just singing, but storytelling & poetry, dance, and theatre too).