Over my admittedly young career in music, I've played with a plethora of musicians in a plethora of different settings. I've sat in with symphony orchestras, played in community and school bands, sat behind the skins of jazz ensembles and combos, and played in a bunch of small ensembles, from brass quintets to rock bands. From all of these experiments, I've noticed that a lot of musicians are the least professional people I've ever met. But you don't have to be that way. Being professional is the best way to assure that you'll get hired, and continue to get hired, as well as creating habits to make you a better player, and a person that your fellow musicians continue to want to associate themselves with. So lets get started.
The Professional Musician is Never Late
This is a big deal, and one that is misunderstood. To be on time, you actually have to be early. Being on time means that you are completely warmed up, tuned up, hooked up, miced up, whatever it is you do, when you want rehearsal or your show to start. If you show up for a 6 pm rehearsal at 6 pm, you're late. Because you will not be ready to play until 6:01, at the earliest, and at that point you will have lost a minute of rehearsal time, time you could have spent making your ensemble better. And if I were organizing a show, and I gave your band an 8pm slot, and you walked into my establishment at 8 o'clock, I'd not-so-politely ask you to leave. I have no time for your tardiness to upset the schedule I created. The reasons not to be late go on and on. If you're late, you let your band down, because they can't start without you, or if they do, their sound will be severely compromised without you. You need to take responsibility for your presence at rehearsal/performance, and be reliable. Nobody wants to work with a musician that doesn't show up for things.
The Professional Musician is Always Prepared
There are two facets to this. The first is that you bring everything you need to rehearsal/performance. This menas all instruments, effects, amps, cables, mics, tabs, picks, straps, etc. etc. etc. I can not tell you the amount of times I've showed up to a rehearsal only to have someone say "Okay, I only have about half the sheet music, and no part for (insert musician here) so he'll have to read off whoever's part and..." its annoying, its obnoxious, and most importantly, its ineffective and inefficient. There's no way you can accomplish as much as you would have usually if the drummer doesn't have his sticks, or if the guitarist is hooked into a hi-fi because he forgot his amp. If you're playing a show, you need to first check to see what will be provided for you when you get there, and then have a backup plan in case there was an error in communication. You need to foresee any issues that could possibly arrive. Could your amp short out? Could your cable fray or rip or whatever it is cables do? The less room for error there is, the more chances that your performance will be a smooth one.
The second facet is that you come prepared to play your part at rehearsal. That means practice. The rule of thumb is that you need to be able to play your part by the second rehearsal. If you rehearse Monday Wednesday Friday, and you get new music on Monday, that means you need to be able to play it by Wednesday. No excuses. If you don't have to spend the time in rehearsal working out parts because somebody didn't do their job, then you can spend that time working out dynamics, or musical nuances, or whatever you want to make that song really pop. If you're improvising a solo, you need to KNOW the changes. There's no reason why the rhythm guy should be calling out chord names to you as you play. You don't need to work out exactly what you're gonna play, because its improvisation and writing something beforehand kind of defeats the purpose, but not knowing what you're soloing over is called a lack of preparation on your part. The more you do it, the less fun you are to play with, and the more problems you'll have finding a band/gig.
The Professional Musician Uses Discretion
"Dude you suck, what were you thinking?" I have heard that during a rehearsal more than once, and it is just the worst way to go about anything. I don't care if it really did suck, telling a band mate or a fellow musician that is just cause for resentment and fighting. I have three problems with the above statement, and I'll tell you exactly what they are. Number one is that it was antagonistic. It was a personal attack on the musician, and is bound to be taken personally. Number two is that it offered no specifics as to what was unacceptable. "You suck" doesn't tell me if I missed notes, was flat/sharp, was not in dynamic balance with the ensemble, was out of rhythm, wasn't clean, or whatever. There's so many possibilities for things I could have done wrong, and "you suck" isn't any of them. And finally, "you suck" does nothing to help me fix my problem. Again, if I was flat, tell me on which notes and I'll fix it. If I missed a note, tell me which one, or ballpark it, and I'll fix it. If I was out of time, give me a hand with helping me get back in time. Playing with a non-conductor-led ensemble is much different than playing with a conductor. In that situation, the conductor addresses the problems with the performance, and you really get kind of a dictatorship. When you all play together, you're in a democracy, and you have to keep the peace and learn how to work together. Everyone gets to make suggestions, and you respectfully and quickly resolve conflicts or differences of opinions. You have to realize that you won't get your way every time, but you have a right to have your opinion heard. So again, be courteous, don't attack any of your fellow musicians, and always make your rehearsals enjoyable.
The Professional Musician is an Ambassador of Music
This one is a pet peeve of mine. Any time you perform in public, the people who watch you form an opinion about musicians. So do what you do on stage, but don't ever act like you're better than anybody in the audience, like any show is "beneath your standards," or whatever. Be courteous to the people who booked you, to anybody who is nice enough to set up your equipment, ESPECIALLY if they aren't being payed, fans who want to talk to you, engineers in the recording studio, and fellow musicians. You never know who you're talking to. The person who booked you is an invaluable contact if you ever need a gig again, plus he might reccomend you to other people. Somebody else in the audience might know somebody who needs a band, or, if you have albums out, will want to buy your album. But, if you act like a bunch of idiots, he/she might not. The engineers in the recording studio are working pretty hard to make your project sound awesome. Don't disrespect them. And your fellow musicians (along with most recording engineers) and you share a bond. You create music, and therefore, you're in the same game. The music business is tough. Don't make it any harder on yourself.
The Professional Musician is Musically Educated
I'm not saying you need a college degree. But, if you want to intelligently and coherently create and discuss music, you should be educated in the subject. So learn some music theory, and always be listening to as much music as you can get your hands on, from all genres. Notice, ALL genres. That means Beethoven, Bach, Mozart, Stravinsky, Wagner, yeah, all those guys. And don't forget about Gershwin, Duke Ellington, Benny Goodman, Coltrane, Miles Davis, Monk. There is a LOT of music out there, and listening never hurt. It often expands your "tool box" and gives you a bunch of new ideas to try.
The Professional Musician Realizes that His/Her Job is No Excuse for a "Rock n' Roll Lifestyle"
Look, I get it. We love partying. But don't be an idiot. Don't trash hotel rooms, don't show up high or drunk to rehearsal or shows. If you want to party, that's awesome, but mess up your own stuff. Don't ever do it in public, because remember, you are an ambassador to music. Like I said, don't be an idiot.
Like I said before, professionalism is severely lacking in a lot of musicians nowadays. Don't be that way. Take care of business, and do it in a professional manner. Just like you have to dress for who you want to be, you have to act that way as well. You wanna be a professional musician? Well, act like it. It certainly can't hurt, and it'll almost certainly help.
Good luck, and have fun!