First rule I start with after learning the first three chords is that 90% of the songs they want can be worked on those three.

Choose a few simple but different ones and demonstrate how G, C and D can play a rolling chanty, a loping cowhand tune, a blues and a Childs ballad just by modulating timing and phrasing.

For beginners, this is usually an eye-opener because they come in thinking that every song is different, and you've shown them the patterns of similarity hidden within.

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