Well... my second 2p comin here
"Fuggle zig zom shwex drigkiy", however, is similarly 'improvised', but without using any kind of 'code "Red Bottom
here your using codes but just less so that you were before - eg Fuggle is based on the english language double g, L, E makes sense to anyone who speaks english, and so we can say it, pronounce it, understand it.
In a way music is the same, we all use codes, theres a set of 12 semitones (bends, quater tones etc aside) that are used for the majority of the time, and things like beats in a bar, chord sequences, falling from a 5th to the tonic because it sounds resolved are all going to be used in improvisation, and so yes in this sense its not new. On the other hand, one solo will probably be unique as a whole. It just depends how far you break it down.
This, just like your word, and your sentence can be copied/imitated, or someone can take just a little bit of it and come up with something new from there. But codes are still needed for listeners, as in speakers of Fuggle, to understand. Even the very free-est jazz has some codes behind it, be they unconventional, so that the audience can understand and enjoy it.
All I'm saying is, while very very few people can create something entirely brand spanking new, without re-inventing western music as we know it, (think free jazz influenced by say eastern traditions in music - they were using rules, just different to those the western audiences were used to so it seemed new and radical) all new ideas come from something that has gone before, thats how ideas work. It doesnt mean that somethings not new. Think how jazz itself came about.
Improv is still improv even though it uses codes and conventions. Not sure I agree with the grading of improvisation- just beacuse something is more original than something else doesnt make it more improvised, it just makes it more advanced/new/original/brilliant/god awful sounding. Improvisation is simply a spontaneous creation with a very small time span between conception and actualisation:
Composition is something created and worked on and developed over time, using developing and breaking musical conventions. Composers all have set styles, set techniques they liked to use that they'd developed over time, and little tricks they put in to impress audiences.
Impovisation is the same, just without the aid of and eraser.
Sorry if thats very long winded, and its only my 2ps worth, so feel free to arrgue back - nothing beats a good discussion.
Oli
PS:
If there are infinite possiblities, there can never be any less left to create.