I've been playing/practising the Pink Panther theme for some time now, but always play from the music. I thought I'd have a go at playing from memory last night. It was quite hard, but I did eventually get it, but I expect I'll have forgotten it again next time I try.
What is it you remember when playing from memory? Is it the tune, notes, fingerings...?
For me, it was the fingerings I was remembering although I started off trying to visualise the music from the book.
For me I think it is mostly the tune and/or phrases, and I know I get a 'feel' for the fingering on some of the faster or more difficult phrases which I tend to practice with the music initially. I know its not the fingering on its own as I have tried to finger tunes without any sound and it doesn't work for me at all.
Things I have found hard to play 'with the music' due to difficult fingering or fast fingering are always easier when I am not trying to read the phrase - once I've learned it.
Also the 'sound' of the intervals which I am trying to use to allow me to then play the tune in other keys. I started this with things like 'happy birthday' but am now doing so with proper tunes like 'My Favourite Things'. It is hard though.
I've been working with my teacher on this and also with my improvised solos which I have been doing part by ear (just play it first to hear the 'sound') and also writing the notation and trying to stick to say just vertical or just horizontal improvising. I've been amazed at how much I can remember and how much easier it is becoming to 'ad lib' during recall - hey that's nearly proper improvisation!
The more I do it the easier it is getting to remember. I have also started carrying a little notebook to write down any 'riffs' I hear that I like the sound of. Again, the more I do this the easier I am finding it.
Transcribing from solos is helping too, though again I find this very hard.
What I would say though is I never visualise the music but the more I sight read, the more I am beginning to recognise patterns - scalar, arpeggios, and chromatic movement, repeats of phrases and those that have moved up/down by a semi-tone, tone, etc.