Jordan Mayberry (DUNCE)

I am familiar with the repeat sign, which indicates repetition only twice, but I noticed in a lot of Steve Reich compositions that there were melody repetitions that could last up to 20 full minutes. Which got me asking: Is there a special notation for repeating sections more than twice? Or do these repetitive compositions simply utilize pages upon pages of the same 2-4 bars?

This is a 3 piece collection of raw sound based music for electronics, the first two of which are more akin to pre-70s early electronic compositions, the last being a more traditional with the inclusion of well, actual musical notes.

Wouldn't even call this my style but I still thoroughly enjoyed it, to my surprise.

So, I'm self taught in musical notation and identifying music symbols, but haven't ever read a full score. I have one important question that I can't find the answer to. Where (in sheet music) is there in indication where specific sets if instrumentation start and finish? For example, there is a percussion section and a strings section, the percussion section starts first and the strings come in later. Since I wouldn't imagine there would be 3 full pages of rests in the sheet music for the strings that start late (that would be insanely inefficient and a waste of paper), what would indicate the starting point for this late instrumentation? Thanks in advance.