Yes, I find bass + (backing) vocals tricky too. I realized that I either sang something fairly intelligent but played “EEEE/GGGG/DDDD” stuff or else played a reasonable riff and sang “Shoop shoop, shubarb-barb a lem alem”.

For me, the problem was that all my integrated guitar work fell apart as I started to think about what I’d have to do with my mouth. Like Sark suggests, I found things got better once we recorded stuff. I’d play it in the car, singing ever more ambitiously and confidently until the lines were 2nd nature. Seeing as the basslines already were, the two knitted together a lot easier and I was less worried at gigs.

For some people, playing and singing at the same time is just as easy as breathing, but for others it takes a little more work.

I had this trouble too when I first started. For me, I found that the easiest thing to do was to listen carefully to the piece I was playing and just sing the lyrics in my head for a few time through, just to make a ‘mental note’ of where the important changes in the vocal happen; then it’s just practice, practice, practice.

After you have one or two songs you feel comfortable with, you should find that others follow fairly easily. Try to start off with songs that you can play almost in your sleep, because you almost have to let that part of your brain that is playing the tune run on auto while you concentrate on putting the emphasis on the vocal.

Good Luck.