If the actor John Williams made another “Timeless Classics” commercial…
“I’m sure you recognize this lovely melody as ‘All By Myself‘. But did you know that the original theme is from the 2nd movement of Rachmaninoff’s Piano Concerto No. 2?”
Heh. Musicians comping from other musicians is as old as music itself. The piano part here may look a little funky though. This is because it’s a conductor’s score and everything that can be condensed is on condensed staves. In fact, there are two pianos in this piece, sharing a pair of common bass and treble clefs. A player’s score would be different, with the voices broken out with separate scores per player.
One of the downsides of rendering from a condensed score is sometimes the realism of the piece is slightly affected. There is always a slight difference in timing when two (or more) human players play a part. Most folks won’t notice this, but if you’ve done any music at all using a sequencer, you are cursed with noticing it. The solution is to split the condensed voices into individual players. To do this, you must pay attention to note stem direction, and sometimes intuition because there are cases where two notes at the same position on a stave will have the same stem direction but are intended as separate voices for individual performers and not a polyphonic chord for a single player. This isn’t an issue for most orchestral instruments as they are monophonic and incapable of chords – it’s implicit that multiple notes mean multiple players. Pianos however ARE polyphonic, and that makes for some interesting notation if two or more are one condensed stave. (Is that chord for one player, or is it a split voice for two?)
You really need to pay attention to score notations such as a.2, a.3, divisi, solo and such as those notations also indicate what is to be done as well.