I can't understand the relationship between MIDI controller message 0x07 (overall volume channel) and MIDI controller message 0x0B (expression volume). I see the latter can be used for crescendo and diminuendo, but given it has values ranging from 0 to 127, what is the default value and how these values are relative to the former?
Let's say I fix volume for channel 1 to 100 with a CC 0x07 at the beginning and never change it. How do I implement a diminuendo by sending CC 0x0B messages periodically? What is the first value of CC 0x0B I should send? 100 or 127, assuming expression is a percentage of volume? And what if I want to do a crescendo instead?