I’ve been to seminars, classes, and you have too, and this has come up. People I love and respect have differing opinions. But here is mine.
1. There are two kinds of auditions: The kind where you are one of hundreds of people all paying $35 dollars to be heard for about 3-5 minutes, if you're lucky. And then there is the kind where a director or conductor are taking time to hear singers on their turf (a church, or the university where they teach) on a smaller scale, maybe it's even just you they've agreed to hear.
Note the difference. One audition involves the singer paying. One doesn't.
2. Consider for a moment that it is probably a part of a conductor/artistic director/etc.'s job to listen to auditions, because they rely on singers to perform the things that they want to direct or conduct. They need us to make their vision for their company, choir, etc. a reality. Please remember that you, too, are very important to the process of creating a show.
3. However, if I have asked for something out of the ordinary, such as special accommodation of my schedule that was not part of the original block of time alotted for the auditions, and it was granted, that deserves acknowledgement. It is not to be taken for granted that musicians are by far the busiest, most tightly-scheduled people I know, and if someone gave you any extra time, fit you in, it's a big deal. No really. If someone has gone out of their way for you, show your appreciation, and they just might become your biggest fan.
4. I admit, I'm a person who's kind of into thank-you notes in the first place. I think they are polite, I think it shows respect, thoughtfulness, and generally, that you care.
5. I have often noted (no pun intended) that while I do feel especially lucky to have gotten an audition when there are lots and lots of applicants for something like a YAP, I have, in almost every case (with the lovely notable exceptions such as St. Louis and Santa Fe), paid a non-refundable fee, taken time off from my job, paid for a bus ticket, and numerous other costly things to get to that audition that I am very lucky to have. Are they really doing me the favor? In that situation I suppose the reason to send a thank you note would simply be to hope that you might jog the memories of the people that heard you and to remind them that you actually did come, that you were there, that you exist, and that you sang, X, Y and Z. Although, there is a very good chance that if you just sang musically, in tune, all the right notes, with delightful and engaging acting, you would stand out from the crowd on your own.
6. There is something that feels, don’t kill me, a bit desperate about writing a thank-you note under the above circumstances. I’ve done it. And for some reason, it didn’t really leave me feeling warm and fuzzy. If everyone is sending them, do you think that it really is making a difference for you? If the answer is yes, then, by all means do it, but I suppose that I am starting to feel like singers, but sopranos specifically, need to stop living from a place of fear, and start living from a place of “Let me share this aria with you and remind you why humans have never gotten tired of hearing it after three hundred years, let me share myself, my heart, and who I am, and you will want to send me a thank-you note when I am finished.“ I am constantly reminding myself, in singing and in life, that I have nothing to prove. I do not have to prove that I am cool, that I am smart, or that I am the best singer you have ever heard. My job is only to do my work, be nice, and be me. I think a lot of times the bad feelings start and the thoughts about needing to be reminding and asking and sending things, after you have sung your aria and a half, poured your soul out on the floor, and they are still sitting there expressionless saying thank you for coming. It’s okay. There's dignity in showing up. You did your part. Walk out the door and get a coffee or better yet wine, and go home. It’s life. And it’s the one we chose.