I am looking at a piece of sheet music and it has 2 sets of quintuplet 16th notes, and a set of sextuplet 16th notes, all noted together as a triplet..  like there's 2 sets of 5 sixteenth notes with the little bracket and a 5 over each group, and then six sixteenth notes with a little bracket and a 6, and then over all 3 groups there's one long bracket with a 3... what is this mean? Ive never seen a tuplet inside of a tuplet before... How am I supposed to play that?
tuplets actually have a hidden number. any time you see the "3" for triplet, it's actually shorthand for "3:2" which means '3 notes in the time there would normally be 2 of these.' when 5's and 6's are used, it can be ambiguous whether it means 5:2 or 5:4, but regardless it is easy to figure out by looking at the context. but the time under the triplet bracket should be divided in 3, and then each of those thirds divided into 5, 5, and 6. or, for a reasonable human, just play 16 (oh wow, just realized the strange implications of this) notes in that time .... So really all this is saying is, play it like 32nd notes (or 16ths, depending on whether the triplet bracket takes up a whole bar or half a bar, that you can discern by looking at what else is in the bar)... so yeah basically the only technical difference between this and 32nd notes is basically they are just asking you to play the first 10 notes slower by an extremely negligible and unnoticeable amount. unless of course the rest of the music is in triplets anyway, in which case it would be normal to divide it in 3's. a lot of questions here that the context will answer. such as the tempo, and what the notes are