RapidComposer v2.3 was used in these excellent tutorials. The user interface was improved since version 2.3 but these tutorials are still useful today.
Part 1 (Introduction)
Part 2 (Working With Phrases, Chords, Variations)
Part 3 (Idea Tool: brief rundown)
Part 4 (8-bit video game instant music creation fun)
Part 5 (Melody Generator, RC as VST over audio loop)
Part 6 (Tips & Tricks: 15 total)
Part 7: Structure Inspector
Part 8: Building a Composition Part by Part
Part 9A: Generators & Phrase Parameters (and a little tweaking)