It depends on who can instruct you in the instrument and what kind of music you are playing. I've had a totally non-musical friend back us up on the electric bass after about 10-15 minutes instruction on country waltzes. ("OK, Start with this note, when we sing 'away' hit that note, next line go back to the first note, then on the last line go dum-dum-dum on these three. Got it?")