The "Big" Symphony Orchestra vs. the (small or less professional?) Ballet Orchestra...
For twenty years I have tried to find a recording of Swan Lake that was complete, with the full beautiful sound produced by a major orchestra. (In fact, I've always loved Tchaikovsky because he uses almost every instrument in his scores.) So currently I have 3 versions by 3 different Symphony Orchestras, and I can never listen to any of them without every muscle cringing because the tempos are either undanceable (usually too fast) or vary from piece to piece/variation to variation, destroying any continuity of action.

My trade-off for wanting to hear a particular variation not usually performed, or to hear it in the context of the original Act in which it appeared. At least I knew the Vienna orchestra soundtrack of the Nureyev/Fonteyn SL was correct tempo since they had to dance to it. Or, I assumed the same for my Bolshoi recording of R&J.
Last November, I went to a concert by our local Symphony Orchestra thematically concerned with "Russian' music/composers. Both Tchaikovsky's Black Swan pdd, and a VERY extensive selection from Prokofiev's R&J (doing most of the major plot points by excerpting from ALL three orchestral suites Prokofiev had originally created for concert performance.) Knowing of this program ahead of time, I had contacted the conductor and orchestra staff to insure that they were played at correct dance(able) tempos. And luckily our conductor had worked previously for several years in Vienna (with the State Opera Orchestra I believe) and so had conducted numerous ballet performances and understood my concern. I was satisfied by the results when I attended the concert.
Smaller ballet companies are usually relegated to using pre-recorded music, or a "pick-up" orchestra, but I also remember larger companies doing the same. For example, I remember ABT bringing it's conductor on tour to Los Angeles, but not their orchestra, and so having to rely on the same "pick-up" of experienced (or not) instrumentalists. I believe the Joffrey did the same, or used mostly recorded music for many pieces.
If those orchestra players had also worked in the film industry, at least they should have been experienced with quick tempo changes. (Which always makes me wonder why no one thinks to use film composers to produce new ballet scores since they are so experienced with variations in length and tempi and conveying dramatic info thru music. Though Goldenthal's score for Othello is not my favorite.)
I also remember the L.A.Philarmonic complaining (c. mid '80's) about having to share the Music Center/Dorothy Chandler Pavillion dressing rooms with visiting dance companies and having to endure "smelly tights drying in the bathrooms". One of the reasons I think those dance companies were very glad to decamp to the OCPAC when it finally became available. And now the OCPAC, too, has constructed a separate concert hall, so their OC Orchestra doesn't have to share the space either.
Of course I recently witnessed an orchestra's unaccostumed speed forcing a dancer to compensate it mid-performance of a variation. It made me wonder if there had been a rehearsal before-hand, or any opportunity for the dancer(s) to "fine-tune" this with the orchestra.
BTW: Does anyone remember a famous female dancer (?) stopping mid-performance (or hopefully just a dress-rehearsal) of Don Q (?)to stalk off the stage because the tempo was wrong? I definately remember the "diva" attitude, but understood her frustration, and the controversey it produced. (Maybe that was the last time journalistic complaints about ballet orchestras 'reached a crescendo'.)
Q: Why is it always the horns? The woodwinds might have problems occasionally, but the horns?