It is called bitonality. You can always say it's avant-garde music and the listener is just not up-to-date.

Buskers who are not up to their task are quite common, alas. Some just don't realize, others don't care as long as the pennies flow.

Forgot to put the capo? Yes, I did that once, and realized only after the first chord. Advice: keep smiling and place the capo swiftly but without visible haste.