One example from the jazz idiom is Bill Evans' 1963 Conversations With
Myself (Verve 821-984), In the liner notes Evans' makes the following
comments that may be relevant and interesting to the list.

   "...in recording the selections, as I listened to the first track
   while playing the second, and the first two while playing the third,
   the process involved was an artificial duplication of simultaneous
   performance in that each track represented a musical mind responding
   to another musical mind or minds. The argument that the same mind
   was involved in all three performances could be advanced, but I feel
   that this is not quite true. The functions of each track are different,
   and as one in speech feels a different state of mind making statements
   than in rexsponding to statements or commenting on the exchange
   involved in the first two; so I feel that the music here has more
   the quality of a 'trio' than a solo effort.

   Another condition to be considered is the fact that I know my musical
   techniques more thoroughly than any other person, so that, it seems
   to me, I am equipped to respond to my previous musical statements
   with the most accuracy and clarity.

   Yet, I hesitate to state this recorded result is identical to trio
   performance or more valuable aesthetically or in depth or intensity
   of emotion. It is in the end still the product of one subject."

As an aside, when classical pianist Jean-Yves Thibaudet recorded a disc of
Bill Evans' music it included none of the songs from the album, but was
titled Conversations With Bill Evans.

Ed