Answer:
1. How to determine if a beat is 2/4:
- 2/4 time signature is usually determined and identified already on the piece, but if you're talking about media like an audio file, then you need to use your ears.
2/4 sounds like ! .
! = Downbeat
. = Other beats
2. You can find that information usually on the top right corner of the piece.
3. That really depends on the piece. But mostly, change of the tune and melody is rare. You can tell by looking at the key signature of the piece.
You can find all the key signatures online.
4. Here's some additional help:
- Nothing's complex. Really. If you dig and dive deep into it and find the patterns and get used to the melody, it doesn't even matter if it's long anymore.
- You can tell if a piece is long by looking at it's length, if it's 1 page it's super short, if it's 2-6 pages you can say it's medium length, if it's more, then it's long. But this doesn't really matter.
That's all, hope this helped.