The Improvisations - The recordings above are exactly what the name refers to... improvisations. They have been recorded during concerts or recording sessions without any preparation, planning and are definitely not played from a book or sheet music. Most times they are played while the recording crew sets-up the microphones and so the quality of the sound is not always the best. They are played and improvised from the heart!

Wikipedia, the free encyclopedia says:
Improvisation is an important aspect of music in general. Musical improvisers often understand the idiom of one or more musical styles—e.g. blues, rock, folk, jazz—and work within the idiom to express ideas with creativity and originality. Improvisation can take place as a solo performance, or interdependently in ensemble with other players. When done well, it often elicits gratifying emotional responses from the audience. Very few musicians have ever dared to offer fully improvised concerts such as the famous improvised piano recitals by composers/pianists like Franz Liszt, or the origins of Liszt's improvisation in an earlier tradition of playing variations on a theme that was mastered and epitomized by Mozart and Beethoven.