I grew up playing piano. On a staff, I was taught there are 15 keys-- 7 sharps, 7 flats, and one natural (C). However, looking at a piano one can clearly see there are 12 notes. That would mean 12 major / 12 minor keys, right? Most guitarists and bassists I know would say that they practice in all 12 keys. I (try to) practice in all 15 keys. Granted, 3 of those keys are enharmonic, meaning they share the same notes but different names. So even though the shape is the same, the notes are called differently. Yeah, this is nitpicky. But I cringe when I play with guys who don't understand how keys work. It goes something like this... Singer on acoustic: "What key is this in?" Guitarist: "We're in D#" Me: "Let's call it Eb since D# isn't a key." Rest of the band: Gives me a funny look. I don't think either answer is necessarily wrong. But it seems 12 is incomplete. Am I wrong? Does it matter?