Pianist Jon Easton said something I try to bear in mind - we were playing duo every week for awhile, just sessions, and I was talking about how to improvise in a musical way with someone (like Jon) who could hear at a much deeper level than I could. Particularly when that improviser was hearing a much different harmony than originally composed nod was following a melodic line that strayed pretty far afield; I think what I actually said something like 'how do I respond when I can't fully hear where you're going?' Jon said that, first, if what I'm doing is 'responding' I'm not really playing with what's happening, I'm playing with what happened. And second, if what he's doing is improvising music he's hearing based on the melody we've chosen and I'm improvising what I'm hearing with the same melody, then the end result should be musical. We're both hearing the melody, we're both hearing our internal line, we hear each other as that internal unfolds in the air; it's more action and less reaction.