In reply to Blue Straggler:
> I am vaguely picturing plugging in a cheap digital piano to use as a keyboard controller, and the software providing extra "voices", and mucking about putting in some simple melodies that I can maybe loop and layer and put a rhythm track on. A bit like Cubase basics(*) I guess.
> * I last saw Cubase running on an Atari ST or Amiga in 1995, my flatmates were into it
Reaper is great, but may not be your best bet. It doesn't come with any built in instrument sounds. You can download plenty of free ones, but a bit of faff is then required setting them up (getting them in the right directory & then getting reaper to look for them).
It's excellent for recording and editing audio, its essentially free (unlimited trial version / period) but the £50 ish licence is well worth it for the upgrades. It will do everything you want if you don't mind a bit of tinkering, but it's not a plug & play daw.
edited to add: Have a look at some online daw's like bandlab.com that may do what you want - lots of sounds & loops to choose from.
Post edited at 18:18