Conductor's Knowledge: Ithaca 2011, pt. 2

according to CSC, there is a basic typology of beats:
Command
Information
Reaction

the analogous words in most any conducting textbook will be easy to find - i think commonly used are "active" and "passive" (analogous to the first two, with reaction falling in the "active" category). but this is a better typology because it articulates what the response from the musicians is supposed to be.

command is a beat that one expects something to happen right at the ictus of, or one given as something is in the process of happening. in every case, of course, if one wanted to count out loud in time to your pattern they should be able to do so. but this particular type of beat lets one know that you are supposed to say the word out loud, and in ideal cases how loudly and with what sort of articulation. it gives you the impression that the conductor is saying: here. here. here. there is an affirmation of sound.

information is just that, and nothing more. this happens, for example, when one musician, say a concerto player, has an extended solo section that none or very few of the instruments in the orchestra play during. the important thing about information beats is that they let the players know where in the music you are, but never incentivize the orchestra to actually play on any of said beats. the moment someone accidentally comes in (who was at all watching you), your beat has turned from information to a command beat. the information beat is interesting because we often forget when to use it. it is useful in places where the whole orchestra is playing but nothing is happening on a said beat (say if everyone had a half note in a slow tempo). the first beat would be a command beat, but the second beat of the half note would be merely information, because there is no action on it, even though everyone is playing. this is one of the easiest things to forget about using. its inclusion gives one's conducting a sensitive, various look, which avoids the stereotype that the conductor is merely a glorified metronome.

a reaction beat is tricky: it must show that you expect nothing to happen on the actual ictus of the beat, but that you DO expect something to happen directly afterwards (and the quickness with which it happens is manipulable in the gesture as well). usually this involves a slowing or complete stopping on the ictus so one can make the sudden action required to inspire a reaction. the easiest thing to do with this is to forget about the stopping. if one makes the quick motion on the beat, something will happen after, but the difficult part is preventing anything from happening on the beat, which is what the slow motion/stop is for.