A friend lent me one to take on a canoe/camping expedition. The sucking/drawing principle making a different note is similar to the melodeon and anglo concertina. I found playing jigs, reels and morris tunes not too challenging even though I'm a string player. The instrument was very popular with sailors because of its size and inevitably got used for shanties (alongside concertinas, fiddles, bones and the like). So my conclusion is, the harmonica is ideal for folk song and tunes and one tuned for D/G would work well in sessions. Don't get pinned down by trying to find stuff that has been covered by harmonicas, just experiment and get happy!