Symphonic music can be bold and dramatic, or it can be wistful and soft. In all cases, if you can keep noise to a minimum, you will make your experience the best it can be, for you and everyone around you.
You are encouraged to:
Not talk during the performance
Silence all cell phones and pagers
Try to refrain from coughing during quiet musical passages
When do I clap during a performance?
At the beginning of the concert, the concertmaster will come onstage. The audience claps as a welcome, and as a sign of appreciation to all the musicians. After the orchestra tunes, the conductor (and possibly a soloist) will come onstage. Everyone claps to welcome them, too. This is also a good moment to make sure your program is open, so you can see the names of the pieces that will be played and their order.
In most classical concerts—unlike jazz or pop—the audience rarely applauds during the music. They wait until the end of each piece, then let loose with their applause. But this can be a little tricky, because many pieces seem to end several times—in other words, they have several pauses or parts called "movements." These are listed in your program (indented under the title).
Do musicians like applause?
In general, musicians and your fellow listeners prefer not to hear applause during the pauses (movements), so they can concentrate on the progress from one movement to the next. Symphonies and concertos have a momentum that builds from the beginning to the end, through all their movements, and applause can "break the mood," especially when a movement ends quietly. Sometimes, though, the audience just can't restrain itself, and you'll hear a smattering of applause—or a lot of it—during the pause before the next movement. It's perfectly OK to join in if you enjoyed the music too.
When will I know the piece is truly over?
One clue is to watch the conductor. Usually, s/he won't relax between movements, but keep hands raised; the attention of the musicians will remain on the conductor. If in any doubt, it's always safe to wait and follow what the rest of the audience does.
At the end of the piece, it's time to let yourself go and let the musicians know how you felt about their playing. Many pieces end "big"—and you won't have any doubt of what to do when. Some end very quietly, and then you'll see the conductor's hands raised for a few seconds at the end, to "hold the mood." Then the hands will drop, someone will clap or yell "Bravo!"—and that's your cue. There's no need to restrain yourself. If you enjoyed what you heard, you can yell "Bravo!" too.
What if I am late?
If you arrive late to the concert, the ushers will not allow you to be seated until a convenient break in the music. As a courtesy to the orchestra and other audience members, please remain seated throughout the performance. If you need to leave for any reason and return, you will not be seated again until a convenient break in the music.