Let's say I'm soloing over a piece in C Major. The chords are C, Am, F, G - a typical ballad/rock progression. I realized while improvising over this that I kind of think in three modes (which I don't really have names for, but I'll make some up for ease of understanding).

- I have Arpeggio Mode, where I play arpeggios that correspond to each of the chords, maybe spicing them up a bit like a Cmaj7b9, Am9, Fmaj7, and G7b9 with little runs to connect the arpeggios.
- I have Major Scalar Mode, where I just play away with the C Major, Bebop or Major Pentatonic scales.
- And finally Minor Scalar Mode, where I play C Minor Pentatonic or Blues scales.

I usually switch between these modes while improvising, but I realized that if I mix the modes (especially Major/Minor Scalar Modes) I come up with a scale kind of like this...
C, Db, D, Eb, E, F, Gb, G, Ab, A, Bb, B. Now, looking at this, I realize that this is the chromatic scale, so I come to the conclusion (which has taken me two and a half years to reach) that you can play ANY NOTE AT ALL over a chord progression. Now I feel like I've wasted my time learning all those scales and such, but then again, had I not learned those scales and such, I may have never noticed this...

Anyone that has something to add, something to correct me on, or if you want to tell me how you experienced a revelation due to my preaching above, feel free to comment.