What it sounds like when I'm travelling at the speed of sound totally hypothetical here: 
lets say a man is playing a song on a guitar and I begin travelling quickly away from the guitar, if I were to reach the speed of sound, what will I hear? (my assumption is that I will hear a single note humming in a constant state...like pressing a key on a synth). 
assume im not in a vehicle and the sound of air wizzing past me isn't involved...not a practical situation, just hypothetical. 
total noob here, my apologies. 
and to take it a step further...if i can speed up or slow down (move forward or backward) ever so slightly from the current note "im in", then back to the speed of sound at another note, would this be possible?...to move from one note of the song to another?
 A: 
my assumption is that I will hear a single note humming in a constant state.

A sound wave is not a thing that you can hear.  Assume for a moment that you are just standing in the coffee shop, enjoying the music.  What you are hearing is not the waves.  What you are hearing is the guitar.
The waves carry acoustic energy from the guitar to your ear.  The guitar causes fluctuations in the pressure of the air that immediately surrounds it.  "Wave" is our word for how those fluctuations propagate through the air.  Your eardrum experiences the same fluctuations as the wave passes by, and you hear the sound.
If you could somehow magically keep pace with the waves and not feel the supersonic blast of wind in your face then you would hear nothing because the wave is not passing you by.  You would experience only the steady-state pressure of one peak of the wave or one trough.  As far as your ears are concerned, a steady-state pressure equals silence.
A: I'm pretty sure you will hear nothing from the guitar, because you will be traveling at the same speed as the sound so the sound wave will not be able to make vibrations on your eardrum thus you hear nothing.
A: You would hear Whoosh... and Boom!  The sound of air rushing past your ears traveling at the speed of sound and the shock waves would entirely drown out the sound of any guitar even with the most powerful amps! ;)
And if you say well then remove the air and do the experiment in space - you will not hear any sound since it requires the air to propagate. ;) ;)
But assuming you could somehow overcome the more practical issues, the answer is you would not hear the sound at all as Bob Bills says. Even if the guitar started playing before you took off - when you reached sonic speed the guitar sound waves would be Doppler shifted to zero frequency.
