I want to convert an existing audio bass track to midi, so that I can edit and embellish it. I will then convert to audio. Does Reaper have this capability? If not, does anyone know of a utility that can do this? Thanks.

Check out reatune in the cockos plugins. It does pitch to midi.

Thanks Fritz, I'll give that a try and report back.

The most accurate I've used so far for monophonic material has been "midifier" (which is quite cheap) as it also does the vibrato and portamento of notes quite well so you can really get expressive with it. The only problem is it doesn't report latency well but using voxengo's latency plugin after it makes it work fine :)

piz audio2cc can be used for volume tracking, this coupled with reatune and snap to scale is quite powerful in concept

Junction may suit your needs:

Great forum support 

Thanks very much to everyone who provided advice on this topic. Best forum experience I have had to date. Good on ya.