Anything here will be inserted into the <CsOrchestra> section of the .CSD file before anything generated by the orchestra. things like global variables or gui instrumet definitions should go here.

anything here will be inserted into <CsScore> section of the .CSD file before anything generated by the score timeline. the global score's processing is done outside of the score timelines, so any notes put here are not factored into values calculated from the timeline, like total duration, nor are any notes in the global score section translated like the timeline is when a different start time is used other than 0.0. for instance, if you use 2.0 as a start time, a note in the score timeline at 2.0 will be translated to start at 0.0, while a note with a start time of 2.0 in the global score section is not affected and will start at time 2.0.

there are also certain variables made available from blue (blue variables) that are useful for specific purposes. one of them is <TOTAL_DUR>. an example of it's use is:

i20 0 [<TOTAL_DUR> + 10] .95 1 1000

the note give above is for a global effect(a global reverb unit). this note will always start at time zero regardless of when i start playing the score, and will always last as long as the duration of the generated score from the timeline plus 10 seconds. because blue variables are a text swap, the above use of the bracket notation that Csound uses was necessary. for a score with a 30second duration, the above note would have been generated as:

i20 0 [20 + 10] .95 1 1000

because of the blue variable used, i never have to change that note again, and i will always have the reverb unit on, regardless of when i start the score to play.

if i had not used the blue variable and put the note in the score timeline, i would have to constantly move the soundObject that had the reverb note to start at a time equal to or great than the play time i designated. (which is why i made the blue variable to use in the first place!)