OK, so... I've got a ton saved up from various orchestras over the last 3-4 years or so, and I finally dug them out.

From my semi-pro orchestra:

"This is - I'm sorry about the wording - a very horny movement." (referring to finale of Schumann's 3rd Symphony)

"The trumpets add some spice, but we need the tikka masala sauce that you bring."

"That was very mariachi."

"Do we have anything that resembles a gong-- NOT THAT WINDOW!"

"Sorry I can't do anything about the piano. It's like we're in a saloon... I feel like drinking some whiskey." (referring to an out-of-tune piano when we temporarily had to rehearse in a different place)

"My kidneys just moved someplace different... just so you know..." (after a fortissimo tuba SPLAT)

"Sul ponticello, please -- get comfortable with the bridge. Don't jump over it... or off of it."

"It needs to have some meat. I just came back from the pampas, the idea of meat is very much on my mind."

"Just remember: Hungarians are the only people who can go into a revolving door behind you and come out in front of you." (on Bartok's Concerto for Orchestra)

"Chorus, I'd prefer if you could get in before... Curtis, the 1st oboe, should not turn blue, please. That would be nice."

"Drive it to the downbeat. Drive it like a truck straight through the Capitol... Wait, that's happened."

"The late night prices don't start until 10pm, and it's a short concert... so we'll play everything a lot slower." (on post-concert drinks)

"We'll play a piece by an Egyptian composer so he can... [faces sideways] ...play in profile." (rehearsing Piazzolla's Suite Punta del Este, referring to the bandoneon projecting its sound mainly to the sides)

"You go from being stuffing to being the main dish. I'm a little hungry, yes, but I shouldn't think about it."

"It's the difference between tomato puree and tomato paste. You're playing puree, we need the paste."

Soloist: "It sounded like a kind of slow angry tango, the 8th notes."
Conductor (a native of Buenos Aires): "I wonder why."

"Draw in a pair of glasses or a New York strip steak, whatever draws your attention to the da capo. I recommend the steak."

"It's loud, but once you get used to it, it's almost like a lullaby."

"Here you're standing somewhere beautiful like Yosemite, and you're like... you couldn't care less about Mirror Lake."

"Play as if you're saying, [sings] 'I think I'm more important than thiiiiiis...'"

"As loud as you can, as wide as you can, as ugly as your teacher would have never wanted you to play."

"They wanted to hear some noise, so I said, 'Come to my dress rehearsal.'" (on his sons being at the dress rehearsal for Varese's Ameriques)

"It's like a worm turning into a butterfly... and then you come in with a bazooka."

Conductor: "Have you been to the junkyard lately?"
Percussionist: "We took the brake drum off your car. I hope it's OK."
Conductor: "Why would it not be? It has to be tuned, though."

"This is 'Psycho' music. Violas, you bring the thing we don't wanna see. WE HAVE TO SEE IT." (miming a slasher-movie stab with the baton)

"We have Mika Pelo here, just in from Berkeley. And now we are going to terrify him with what we've done with his piece."

"You should learn to ignore me completely, like you do all the time anyway."

"If he [the composer] runs away in the middle of the performance, don't take it personally."

"We'll be taking no repeats in the trio. That'll give us two more minutes without tendinitis." (rehearsing Schubert's 9th)

"We'll wait for the Short Ride in a Fast Machine to finish." (hearing a car rev loudly just as he raised his baton at a dress rehearsal for for an outdoor concert, shortly after performing the Adams piece)

"So it's almost disco tempo, not quite."

"This is what composers do in their spare time." (holding up a three-page list of changes the composer wanted to make to a new piece)

"It's a little too rustic, like you have a beer in your hand and you're dancing. I know it's St. Patrick's, but..."

"It's a Haydn concerto for prepared piano and orchestra now." (after something fell into the piano)

"It needs to be more desperate -- at least until the bear comes in, and then maybe a little less. Maybe it's a sweet bear." (going into the "Peasant and Bear" bit of Petrouchka)

From my community orchestra:

"You can't all have your own tempo, you won't feed it, you won't clean up after it, it's just not feasible!"

"Murder and death and all this terrible stuff--and then there's cigarettes!" (referring to Carmen)

"Here we're getting rhythm, and after this we got rhythm." (in a Gershwin medley)

"It's a hemiola. Don't worry, you can get it removed at the doctor's office."

"Let's try to keep it on the softer side of nuclear explosions, OK?"

"And now let's go back to our old friend John Philip Debussy." (referring to Debussy's Scottish March)

"Light and airy, like a souffle... that sounded like a Hot Pocket."

From other, one-off orchestras I've played in recently:

"Play them [sforzandi] like you secretly want to stab me and take my job -- or not so secretly."

"Even more! The damn Judgment Day is near, the trombones are going to throw us all into Putah Creek!"

"The attire for the choir will be... what you would wear to a Log Cabin Republican Christmas party."

"The choir comes in where I was saying blastissimo forte."

"It's like musical blue balls. It goes on for three hours and then the tension is released." (on Wagner)

"We don't want still water, that gives us pollution, mosquitoes, and stuff." ("Scene by the brook" movement of Beethoven's 6th)

"The triplets can be a little more triplety."

Cellist: "What are we wearing?"
Conductor: "Clothes."

"Not a Beethoven forte. We don't want to get excited. We're too bourgeois to get excited. It's beneath us." (rehearsing Mozart)

"It feels like we're on a journey of self-discovery. Or discovery of what's written on the page here." (on playing off hand-copied scores and parts)

"You guys [gestures at celli] are the pasta, and we have capers [violas], olives [2nd violins], anchovies [1st violins], and other stuff [waves broadly at winds/brass] bouncing around in there..."

From my community orchestra, tonight:

"It's important that you look up here every half hour or so."

"It's supposed to be an eccentric dance, but I'm not sure it's THAT eccentric."

Hmm, it's been a while.

Semi-pro orchestra, rehearsing for a program that included an extended version of Tchaikovsky's Sleeping Beauty Suite (the concert suite plus three additional dances from the ballet) and Respighi's Vetrate di Chiesa:

"Make it as rustic as you can -- like a good French bread."

"A nice big fortissimo, please. Let's see if we can set off the alarm again." (an alarm interrupted the rehearsal 15 minutes earlier)

"It's not German music, it's [in Russian accent] Russian trying to be French."

"Vodka before, vodka after, who cares about bowings?"

"Give this a church-like feel. We're all going to confession."

"Violas, why are you so aggressive? It reminds me of some of my favorite guitar moments... electric guitar." (launches into air guitar solo)

Assistant conductor: "Our green room will be called the Purple Room. I know that's confusing..."
Violist: "That's okay, some of us are color-blind anyway."

Semi-pro orchestra, rehearsing for an upcoming concert featuring Mozart's 25th Symphony and Richard Strauss's Don Quixote:

"Piú pesante. Nice and fat, you know?" (on the Sancho Panza theme)

"Give me four bars before 57... five bars, it's cheaper!"

"Ah, the wind machine. Just as Mozart would have wanted." (percussionists were packing up while we rehearsed Mozart)

"We have all these delicate things, and then this annoying, interrupting stuff... that should be you! You need to come in and be as annoying as possible."

"Suddenly, after a few pints of beer, 31 arrives."

"They're on a boat! ....... but they have no oars ....... which is a little bad."

Community orchestra:

"It's very Wagnerian... meets pops!"

"Make the first measure slightly more beautiful... with A-flats."

"Play lushly... like a lush."

"When we see these dotted rhythms, I know we always think it's gotta be short, or the audience will think we're playing triplets and throw pineapples at us, but in this tempo we can play the 16th a little longer..."

"Un poco pesante: a little peasant."

"It's from Wikipedia, so you know it's true."

"How many of you know Vaughan Williams's Fantasia on a Theme of Thomas Tallis? Here is your chance to play three measures of it without having to figure out the rest!"

Just one more to add, now that we're done tilting at windmills:

"This needs to be a lot more scary. The sheep are terrified!"

The sheep quote? That was Christian Baldini, rehearsing Don Quixote. This was, of course "The victorious struggle against the army of the great emperor Alifanfaron"...