En una cancion puede no repetirse una parte?

Creo que cada canción tiene una parte repetitiva. el coro.

Comma should appear after  the quote, 

Material safety data sheetswhen working with any type of chemical the should be posted in a conspicuous place in the work areamsdsif a material does pose a health hazard teachers shouldobserve appropriate precautions when they or their students handle the materialmsds are available fromproduct manufacturesmsds sheets must beavailable in shop/science classes at all times