A length rest will create a rest note. A rest symbol will create a rest note lasting the amount of current length event. In Symbolic Composer it has uses, too, allowing to quantize computed values to musically meaningful rhythmic values. Non-quantized values can also be used. A general quantizer can be applied to all metric classes.
Expressions cover legato , humanize and velocity .
Legato allows randomization of durations. Humanize randomizes note-ons and velocity randomizes velocity values. By default expressions are controlled by brownian noise. This simulates performer's finger noise. Optionally other generators can overpass the brownian noise.