There are a lot of ordinarly people out there who are not in the 'everyone' category and may now become aware of this.
Yet anyother reason not to patronise either.
Really really impressed with this project, and now Munich truly owns their data unlike any other government.
I think you would find it difficult these days to find an OS that could not meet your requirements. However, any software package requires practice (lots of it) to get the most out of it. If the O/P is familiar and comfortable with Linux then why change? Audacity was a good choice for the O/P as a starter, as it has a shallow learning curve. Ardour will do much more (including very valuable non-destructive editing) but will take some time to get to grips with. The version coming out soon will also have extensive MIDI capabilities.
If the O/P is going down the road of keyboard instruments, he/she can save an enormous amount of money and buy a dumb keyboard then link to one of the many excellent free soft-synths - more learning of course, so maybe stick to the accoustic material first then gradually bring in other stuff. A recipe for disaster is to try and do it all at once.
The bottom line is that you don't need a lot of expensive hardware and software to produce first class results, but you do need to know how to make the best use of what you have and, most important of all, you need to develop you musical abilites as far as possible. I have heard astonishingly good music produced on the simplest of kit, and utter rubbish using top-line professional stuff.