"A songs solo changes"
Do you mean repeat the solo over and over again adding bits as I go along? If so - I do this already
Random improv over a solo, or random improv over a song in general. My issue is coming up with something that moves outside of my "box" of scales/licks I do.
I think the only way i'm gonna progress is using modes.
But ty for your input
Check my Blood Brothers cover and you'll see some of my improv.