...I'm glad you paraphrased a little - what I actually can do as a guitar player without an excellent 'ear', is to pretty quickly play any scale or mode you throw at me - G Lydian, E phrygian, C major (my favorite), yada yada yada) - what I have ABSOLUTELY no idea is how and when to use these as I hear a set of changes. Furthermore, I'd like to be given scales and modes for the start/stop points of the chord sets in a song. What I'm looking for is the ability to get my fingers to the right place and at first, just play the straight scale from root to root, and then start to 'improvise' over it - mix the notes up, add arpegios and chromatics, add rests etc. - It's my understanding that this is what good improvisers do in real time when they hear a set of new changes that they need to play over (correct me if I'm wrong) - I want to be able to do that to. After 30 years of playing guitar on and off, I can't even do this at a basic level. I feel a tool such as I describe would help get me to the next level more quickly.