Today's Random Question: Click Tracks

For shows that use click tracks, everyone in the pit hears it. But most of them can create their own mix, turning up and down different tracks (individual instruments, instrument groups, vocals, click track, etc) to customize what they hear during the show. It's not so much about knowing the tempo and cues but really more about keeping everyone together. Plus, there could be any number of substitute musicians or a different conductor at any given performance, so the click helps maintain the same sound no matter who's playing/conducting.

SomethingPeculiar said: "Click-tracks would primarily be used in instances of pre-recorded music combining with the live orchestra, or for some other reason that required the tempo to beexactlythe same every night. (I.E., the pre-recorded vocals in PHANTOM probably have a click track, if the live orchestra is even accompanying those moments.)"

Exactly and most dance shows use prerecorded vocals during the ensemble numbers.

There's a lot of generalization going on here. Like many other things, how clicks are handled is a case-by-case basis.
Sometimes only the conductor hears the click. Sometimes only the drummer. Sometimes conductor and rhythm section. Sometimes everybody hears it whether they want to or not, and sometimes the musicians have control over their individual mix (i.e. Avioms or Roland systems).

Sometimes the "click" is a clicking sounds, sometimes it's (like in the case of Radio City) the sound of somebody counting and occasionally subdividing beats.

The click track could be to line up pre-recorded vocals; pre-recorded drum beats; to prevent dancers or singers from complaining about shifting tempos (it never works); or because some technical element requires the same timing every show.

The click could be triggered by the conductor, drummer, percussionist, keyboard player, sound mixer, or even from the light board. It all depends on the specific need and the technology available at the time.

And to say that "most dance numbers have pre-recorded vocals" is disingenuous. Many do, most do not.