[TimR]

I use Audacity for this.

If I record the accompanying track myself, I add a click track.

Either way, I use an earbud in one ear and sing along with the singer or the accompanying tracks. Audacity is playing the tracks and recording the new one at the same time. I use the H2 as the input microphone directly into Audacity. You may have a better mike. If not this works well.

The reason for the earbud is obvious but I'll say it anyway. I need to hear the singer, but I don't want the recording to pick it up.

There's another skill involved though. It's easy to think we sing with a steady pulse, but be wrong. Practicing with a metronome can help a lot with this, it really points out where our timing is off.