Guitar or piano, it's still just patterns that are generally well burned-in. Study any instrument seriously and you'll play scales enough that they're quite na

Guitar or piano, it's still just patterns that are generally well burned-in. Study any instrument seriously and you'll play scales enough that they're quite natural "forms" that you just lay on the keyboard/fretboard in your imagination. Playing a melody through a different scale pattern (as long as they have the same number of notes... whole tone etc. are off-limits here) is fairly easy. Something with chords, or multiple melodies, and especially if it doesn't stick to its starting key, takes a little more planning ahead (assuming you can't just move up/down the guitar neck, or add a capo... that's of course trivial), but is still mostly applying the same technique - laying the same notes into a slightly different (but very familiar) pattern. This is a really fun singing exercise, BTW, that many people can try (with minimal music training, though you'll need to know how to sing a minor scale first): take a really simple melody in a major key (most children's songs), and sing it in a minor key. Start with something like Row row row your boat or twinkle twinkle, then something like Happy Birthday -- which doesn't start on the first note of the scale -- is more challenging. :)