system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5 why people clap to music on 2 and 4, and why does clapping on 1 and 3 mess musicians up?

I recently saw a montage of musicians stopping their performance to stop crowds from clapping on 1 and 3 and asking/teaching them to clap on 2 and 4. All of them looked like clapping on 1 and 3 was making it more difficult for them. I asked my mother about this who has been first chair for clarinet in many concert bands and she had never heard of this. Any insight would be appreciated.
gpt
American music is based on syncopation, which is when weak/off-beats are stressed. In a bar of four, the strength of each beat goes: *Strong, Weak, Less-strong, Weakest.* 

Different instruments serve different roles in every genre of music. In jazz, the bass is expected to play on beats 1 and 3 at the very least because the bass represents a more harmonic function in the ensemble. A drummer is playing every beat and subdivision in some way, but they are also emphasizing beats 2 and 4, because they hold a rhythmic function. (This way, bass and drums are doing a kind of call-and-response thing which is a trait inherited from various African musics.) Hand Claps, as an instrument, serve a similar function as the drums in that their role is to accent 2 and 4. When you clap on 1 and 3, it sounds unnatural because you are playing agains the role of the instrument in this genre (and in American music in general).