Press button to randomise

[afternoon]

Currently, sequences are regenerated whenever a parameter is changed. For sequence generators which have some randomness as an input, this means that they change dramatically on each parameter change. This makes it impossible to generate a sequence and iterate upon it. For example, by cutting a 16-step sequence down to 8 steps.

It should be possible to control when regeneration happens and which elements are randomised. Some example scenarios:

1. Randomise only melody notes
2. Randomise groove (step velocities)
3. Randomise everything to start a new idea
4. Randomise only one parameter

Probably this could work as follows:

1. Go to the Melody page, press the [RAND] button
2. Go to the Groove page, press [RAND]
3. Long-press [RAND]
4. Hold [RAND] and tweak the encoder for the param(s) you want to randomise