The vertical lines in a sequencer are what slice up musical notes in time. Depending on what resolution you are viewing your sequence at, there can be many variations between how closely the vertical lines are spaced. But before we can look at the divisions of time, we must talk about time signature.
The time signature tells you how many beats are in a bar and what note or rest is equivalent to one beat. Most time signatures are 4/4, but things can get interesting when you change the time signature. Whenever the second (or lower) number of a time signature is 4, this means that one beat is equal to a quarter note. When the second number is 8, one beat is equal to an eighth note.
Get a more detailed explanation.
For a 4/4 time signature:
1 bar = 4 beats (4 quarter notes) = 16 sixteenth notes = 32 thirty-second notes
As you can see, there are many different resolutions that you can split 1 bar into. Typically, resolutions of 1/32 and 1/64 are in the realm of microediting because any change of notes at these divisions will sound very quick.
Say this out loud to get an idea of what 16th notes are like:
“1 e and a 2 e and a 3 e and a 4 e and a”
This whole phrase is equal to one bar. Each utterance equals a 16th note. Count ‘em up, you’ll see that there are 16 separate divisions.
Vary your note lengths: If you want your melodies to be expressive and interesting to listen to, you must vary your note lengths. After drawing a sequence of notes, try altering the length of the notes and shifting them from the left or to the right in the sequencer.
Vary your note velocity: Same as if you’re programming a drum track. Unless you specifically want a track to sound mechanical and computerized, you should randomize your note velocities a bit. All the while, loop your sequence and listen to it as you go. You will get sick of it eventually, and that’s when you know that it’s time for a break.