Basically I’m trying to make piano backing tracks and was wondering if it was possible to change the sound so it was both less dry
I assume you are talking about reverberation (the reflections and short echos that aren’t heard as distinct echos) that you hear in a concert hall?
Audacity has a Reverb effect. Most professional recordings are done in “dead” (sound absorbing) studios with artificial reverb added later. (Solo piano might be an exception and it might often be recorded in a “good room” with careful microphone placement to pick-up the right balance of direct sound and natural reverb.)
You’re the producer and you’re in charge, but in general I’d recommend you “take it easy” because the (IMO) amount of reverb that sounds great in a big hall usually sounds unnatural in a living room. If you’ve ever made a “live” recording you’re probably noticed too much “room sound” when played-back. Sometimes you can get carried away, so it’s a good idea to come-back and listen the next day to make sure you haven’t over-done it.
and so that the dynamic range isn’t as expansive i.e. loud is slightly less loud, and soft is less soft; the range is more compressed.
There are also Compressor and Limiter effects.
Again you may want to “take it easy” because piano is supposed to be a dynamic instrument. But again, you’re the producer so do whatever you want and whatever sounds best to you.
Limiting is a kind of “fast compression”. There are fewer settings/options so it’s easier to experiment with and easier (than compression) to get good results, so I’d start with that. The Audacity limiter is very good and when set to “hard limit” it (apparently) uses look-ahead because it doesn’t distort the waveform. (It will distort when set to “hard clip”.)
Of course, you can also experiment with the compressor.
Every reverb and compressor sounds different. There are LOTS of (free & commercial) 3rd-party plug-ins and “serious producers” have their favorites. (Compression, reverb, and equalization are the most-commonly used effects.) There is a popular free compressor plug-in for Audacity called [u]Chris’s Compressor[/u]. It’s a little “different” than most compressors but I’m sure it’s popular for a good reason.
BTW - Acoustic instruments and solo instruments/voices are difficult to record. In some ways it’s easier to get better results when recording a whole band (or a whole choir, etc.) with more complexity/intensity and fewer quiet/subtle parts.