C major & E minor, e.g.
I believe the answer is:
keys
(Other definitions for keys that I've seen before include "Lock-openers?" , "Bunch of openers?" , "Musical scales" , "Lockers" , "Islands; piano parts" .)
I believe the answer is:
keys
(Other definitions for keys that I've seen before include "Lock-openers?" , "Bunch of openers?" , "Musical scales" , "Lockers" , "Islands; piano parts" .)