Well, I share a house with a fiddler who does a bit of teaching, so I spend a certain amount of time lurking upstairs hearing some godawful beginners scraping away downstairs. And from the evidence of my ears, the tunes that seem to have a built in capacity to sound vaguely like enjoyable music (even when played excruciatingly out of tune by cloth-eared kids) are Cripple Creek in A and Winster Gallop in G(the normal key) or D(beginner's key).