It's allready difficult to mix well 48 tracks,
It should be hell to mix a 1000 tracks
How can you do that ?
Do you put a note per track ?
There are not a 1000 instruments in an orchestra ?
Read this :
http://theidiomaticorchestra.net/14-orchestra-size-and-setting/
"A modern full-scale symphony orchestra consists of approximately one hundred permanent musicians, most often distributed as follows: 16–18 1st violins, 16 2nd violins, 12 violas, 12 cellos, 8 double basses, 4 flutes (one with piccolo as a specialty), 4 oboes (one with English horn as a specialty), 4 clarinets (one with bass clarinet as a specialty, another specializing in high clarinets), 4 bassoons (one with double bassoon as a specialty). In theory, all woodwind players are expected to be able to play all auxiliary instruments in addition to their main instrument. Furthermore 5–8 horns, 4 trumpets, 4 trombones (one with bass trombone as a specialty), 1 tuba, 1 kettledrum player, 3–4 percussionists (of whom at least one must also play kettledrum), 1–2 harps and a keyboard player (piano, celesta, harpsichord, etc.).
Musicians mastering instruments such as saxophone, guitar, bass oboe (heckelphone), ondes martenot, synthesizer, etc., usually do not have a permanent position, but are engaged for special projects or concerts. Similarly, extra players are engaged when a score calls for extended brass, percussion, etc.