There are basically only two ways to carry out metric modulations. Both deal directly with note duration. The first example is when the subdivisions note stay constant. In a switch from say, 4/4 to 12/8, the subdivisions stay constant, and the pulse changes.
In the above example, the SUBDIVISIONS stay the same (1 & 2 & etc.) from one meter to the next. If you are confused, try tapping your foot to the subdivisions from one meter to the next. Notice the counts get further apart at the change.
The second example would be when the pulse stays constant and the duration of the subdivisions change. The same example as above is shown, but with the second type of modulation.
In this example, the COUNTS stay the same (1, 2, 3, 4, etc.) from one meter to the next. In other words, the subdivisions speed up within the counts, which stay at the same tempo. Try tapping your foot to the counts (numbers). Keep them at the same tempo at the meter change and notice that the subdivisions have to speed up to fit in the counts.
