A single-track MIDI file is just a bunch of keyboard note numbers. There is no intrinsic concept of Bass, or Treble, in MIDI. And definitely no concept of Frequencies as such. The piano sound will be tuned to equal temperament. But another instrument might be tuned to a just intonation, meaning the same notes will have slightly different fundamental frequencies.
Not only that, the MIDI note numbers could trigger a piano sound in the traditional way, but could also trigger drums, atonal sound effects, orchestra cresendos, complete song phrases or even control lights.
A piano player might play with both hands way up on the high end of a piano, then do a long cadenza down to the bottom. At all times, the left hand is the "bass", the right hand the "treble". It would take an artifical intelligence algorithm to figure out what's what, it would only work on keyboard playing and it would probably still make mistakes.
There are, of course, tools that transpose to another key, suggest chord cycles to inspire songwriters, etc.
Sonar has a whole bunch of these MIDI tools. Thanks to your post, I started making a list to reply to you, but gave up because I am beginning to realize there's an amazingly large number of them.
I am currently working on a MIDI-intensive project (which is why this caught my attention), but it's becoming clear I can benefit greatly by stopping for a while and just familiarize myself with what's already in Sonar. I remember Craig's Tip of the Week had some MIDI stuff, too. I'll go through that as well.