I know in the 6/8 compound meter, the first beat gets strong downbeat and the second beat gets the weak upbeat. But I am trying to analyze syncopation in a piece, so I want to know how each of the three subdivisions of each beat assigned as strong/weak ?
6 | V ^ ^ v ^ ^ | 8 | 1 2 3 4 5 6 |
6/8 compound time can be thought of as duple meter consisting of two beats to the measure, where the dotted quarter note gets the beat.
6/8 is just a notational simplification -- if Carl Orff's time signatures had caught on we might call this time signature
2/q. (a two on top of a dotted quarter note).
I consider an upbeat to be a subdivision that does not occur on a foot tap. So, according to the diagram above, there are two downbeats (1 and 4 of the subdivision) and four upbeats. The downbeat at the beginning of the measure, obviously, is the stronger one.
Of the upbeats, 3 and 6 are stronger than 2 and 5 because they lead into the next downbeat. If someone mentions "the upbeat on beat 1" for example, they are talking about subdivision 3. While 2 is still technically an upbeat, the "default" mode would be the 3 and 6. If you compare the following two rhythms, you'll find one feels much more natural than the other:
6 |: q e q e :|: e q e q :| 8 |: 1 2 3 4 5 6 :|: 1 2 3 4 5 6 :|