Too-ra-loo-ra-loo-ral2008-09-11, tags: lullaby, duo, easy
I found this beautiful tune on http://www.dulcimers.com/music/midis.shtml. I made the arrangement a little more 'folk band' oriented, moving the cello part to a flute (or clarinet or second concertina). I reworked the bass part a bit so that it sounds more natural for a cello. The guitar can then strum gently along or fill in the harmony, depending on the skill of the musician.
With a little effort, you could turn this in a play-along tune at a concertina workshop, adding a third voice to fill the harmony and hopefully have one or two bariton concertinas for the lower parts.