I think an employer might be more concerned about a prospective employee who has no outside hobbies or distractions. Employers like dedication, but they don't always like workaholics who have no life outside the office
Perhaps listing yourself as a hobbyist musician (who does gigs on the weekends) will work well, shows leadership that you can work in a team oriented environment.
Same goes with people that say that sport is hobby for them in their free time.
...but if your not sure (because it is not relevant) maybe you shouldn't mention it. Honesty is the best policy, you don't want to get in a sticky situation when your employer finds out some time after being employed that you're actually a weekend gigging musician.
Remember, employers are employing human beings, not matrix clones.