Guys, this is difficult. I am 33, smoking for 15 years now, had to quit for a few weeks (vocal polyps surgery), the habit returned.
Things I think will probably work (seen them work on friends)
1) Find out what habits are associated with smoking and quit them the same time. Be it morning cups of cofee, be it beer with friends, try to reduce them also.
2) Smoke a cigarette in the afternoon or night, after work, as a reward for one day of non smoking. "Tips" to yourself are not allowed.
3) Put a transparent jar somewhere and put the daily cost of cigarettes inside. Watch money accummulate fast.
4) Decline every cigarette offer saying "Thanks, I don't smoke". helps to reassure yourself that you are NOT a smoker anymore.
4) Since he is a musician, if possible, try to only play in places that cigarettes are not allowed.
5) Ask a professional for help. When your car breaks, you don't usually fix it yourself, right?
Hope your friend is successful, SemiLiveMusic, and above all, healthy ever after.