I am learning a piece at the moment which is in 4/4, however some bars look like they should be 12/8, and I am confused about the mixing of notation of sometimes triplets sometimes not. Here is the section in question:
Consider bar 48. The right hand is an easily interpretable 4/4. But the bass staff is confusing. Ignoring the whole note in the extra voice, the first things we see are a quarter note rest, then a quarter note, and then two eight notes beamed together. Okay, that's 3 quarters used up of our 4 in 4/4. But there's still some eight note triples (another quarter), followed by three more eight notes.
So counting the left hand in 4/4 makes no sense. But, if we ignore the triplet of the third beat, then counting the left hand in 12/8 does make sense (albeit with bad beaming). But then the right and left hands don't match up in time properly. What am I missing here? To play this I've counted both staves as 12/8 (while playing the right hand notes as if they are dotted), but I am not certain how accurate I am being (and the original piece is very fast, so I can't figure it out by ear).
Then take bar 50. Right hand looks like a 12/8 (not paying attention to meter at the moment), left hand looks like a 4/4. Is the rule "because triplets are notated in one staff, if there's vertical alignment with quarter notes of the other staff, then it implies triplets in the other staff"? Or am I missing something else?