I think I have a pretty good methodology that I'm using with her. We are sometimes using the notes on the guitar to get her starting pitch, or to remind her how high a particular note is, but since she's more interested in accompaniment than single note playing, we are mostly focussed on playing the chords.

When we work on the singing, we put down the guitars and she sings back to me. I find it's much easier for students to match another human voice than an instrument. The only problem is if your voices are in very different registers, as they usually are if one of you is a woman and one is a man. I have one male student that I work on singing with, and I use the guitar more with him because of that issue.

But I'm still interested in songs that have a limited note range. Any thoughts?