Maybe this post would be better suited for !musicproduction@sh.itjust.works ?
I used Ardour, an entire open source DAW. Definitely more powerful than Audacity for this kind of thing, and I'm much more comfortable with MIDI notation than traditional music notation, too. I did eventually switch to Bitwig though, because I use a lot of samples and synth plugins and Bitwig's workflow and UI for that is just a lot better than Ardour's.
There are quite a few pretty good open source VST/LV2 plugins, e.g. ZynAddSubFX is a really powerful software synth and Dragonfly Reverb is a neat reverb. There are more, unfortunately many open source plugins are only available in LV2 format and unfortunately Bitwig doesn't support LV2.