I know who the teacher GlassHarmonica is talking about, and professional musicians well out of school go to him for help, I know professional musicians from some pretty high level orchestras who work with him when they are preparing pieces the orchestra will play. I think the point is with auditions that if excerpts are being used, it certainly can’t hurt to get coaching. It does depend on the teacher as well, but for example, if you graduated from conservatory 10 years before, and are a bassoonist facing an audition with a major orchestra, and you know one of the main pieces will be the opening of “The Rite of Spring”, having someone work with you on the excerpt will be an added edge.
The way I put it to other people is getting through an audition , whether admissions to a conservatory/music school, or perhaps auditioning for a professional job, it comes down to ‘the edges’ you have. If you audition at a music school and have had exposure to teachers there, it can make getting a teacher to teach you easier (for schools where admission is predicated on studio admission), so summer programs or sample lessons may give an edge. If you are a wind or brass player having played a piece before might be an edge, or someone to work with you on excerpts might be another edge. I have had people tell me that kids get into music schools cold, without having met the teachers, and that is true, but I also know kids who have gotten into schools because they had prior exposure to the teacher and it made them willing to teach the kid…
The point is there is no ‘magic way’, and most of us with kids in music programs come to realize you do the best you can at each step, navigate as best as you can and hope it works out. I don’t think playing in a particular youth orchestra will necessarily help getting into a conservatory (unless, for example, said youth orchestra has master classes, and the kid in it gets to play for X, who teaches at school Y, where they are applying), but on the other hand, the good youth orchestras require auditions, to get in and seating auditions, and that is great practice, plus in playing in a youth orchestra, you learn ensemble playing which will help down the road. In the violin world, there are a lot of students, some really excellent players, who quite frankly stink at ensemble playing, because their focus was on individual solo rep. Music school admissions for violins don’t use excerpts much if at all (none of the schools my S looked at did), so these kids get into the best schools, but then are hit with the reality that most music is ensemble playing, and often struggle and have a hard time, so that YO experience can be huge down the road.
My S had a friend who thought that he had it made, went to the same pre college program, had one of the more highly regarded teachers, did all the ‘right’ things with competitions and such…and when he auditioned for conservatories and music schools, he failed to get into a lot of them, including the one he had been in the pre college program in…looking at him, a lot of people would assume he was a shoe in to get into the big programs, but he didn’t.