[FrankHudson]

I don't know exactly what your budget or expectations are or what equipment you might have on hand, but when I read your post the first thing that came to mind was a looper pedal. For what you mention, even the least expensive could probably serve your needs.

You'd need a pickup or mic for your guitar. The inexpensive (and decent sounding) iRig Acoustic Stage clip in microphone would work. So would a soundhole pickup. And if your guitar has a pickup already, so much the better.

You need the looper pedal.

You need something to amplify what comes out and through the looper and maybe an adapter to hook up from the 1/4 out plug on the looper to that amplification/speaker. Some loopers, or pedals that include looping as a feature, will drive headphones, which would be another option.

What would the advantage of this setup? Well let's say that your briefly stated question means that you want to practice a little chord playing and then practice a little melody/lead playing on top of it in the same practice session. You want to exercise both skills, and you don't want a lot "overhead" in getting to that. You might even want to be interactive in your practice session, as in "Gee that sounded interesting, now what if I use this chord substitution or change something else in the cadence, what would I play over that?" With a looper pedal this sort of thing is natural. You simply record another loop and try your "lead", and the same applies if you don't get the chords right the first time, you just dump it and try again. Having a footswitch makes it's easier to be your own "recording engineer" when you're creating the backing loop on the fly too.

Of course, I may completely misunderstand what you're aiming for too.