Forum: music.stackexchange.com
Tags: <terminology>
Title: What is it called when a song starts with few instruments, and gradually adds one at a time?
Question: Many songs will start with only a few number of instruments, and after a specified amount of time has passed a new instrument is added, and this is repeated until all instruments for the song are playing its rhythms. Sometimes this is also done when finishing the song, but in reverse order.  Does this style of opening a piece has a name?

Answers:
sents: text: Technically, this is less about form and more about orchestration .
text: People can use instruments to denote a shift or division or a new section in the piece, though they don't have to.
text: Orchestration is the art of timbre.
text: When instruments enter one at a time, their entrances are described as "staggered".
text: The fact that the instruments enter halfway through the piece is an orchestrational one.
text: Canons and Rounds do not apply in this context if the staggered voices do not also enter through imitation as well.
answer_details: author: music.stackexchange.com/users/3518/jjmusicnotes
score: 17
sents: text: Development , or buildup?
text: Crescendo is when the music gets louder.
text: Development is nearer to what you ask.
answer_details: author: music.stackexchange.com/users/8828/atoth
score: 3
sents: text: Though this technique does occur in "composed" music - Ravel's "Bolero" and (in reverse)
text: Haydn's "Farewell" symphony
text: - it's more typical of music "constructed" in a sequencer.
text: Because a sequencer makes it easy to work in this way
text: - set up a drum loop, add a bass, add a guitar
text: - you're right
text: , we hear this done far too often!
text: I don't think there's an accepted term for it.
text: "Layering" perhaps.
answer_details: author: music.stackexchange.com/users/17003/Laurence Payne
score: 3
sents: text: The closest term I found for this was a canon .
text: Not exactly the same, but pretty close.
text: A canon pretty much when one voice has the melody and some duration later another voice comes in playing the same melody and then the pattern continues for more voices.
text: A round is also a type of canon that may be slightly closer to what you are thinking of.
answer_details: author: music.stackexchange.com/users/7222/Dom
score: 2
sents: text: I think you can call this a " Mannheim Crescendo ".
text: I also have a teacher who use a french expression to name it, a "crescendo d'orchestre", but I don't find sources for this denomination.
answer_details: author: music.stackexchange.com/users/26154/Sandra-Émilie
score: 1
sents: text: I don't think you'll find an exact term for this, but what you are referring to is "texture."
text: In the type of piece you describe, the texture starts "thin" and then layers or builds to a "dense" texture.
text: For the reverse(at the end of the piece)
text: you could describe the texture as "thinning out" or "layering out.
text: " If there is one instrument, the texture is monophonic, two is biphonic, and 3 or more polyphonic.
text: More info: texture on Wikipedia.
answer_details: author: music.stackexchange.com/users/12700/user3861339
score: 0

Summary of the answers:
When instruments enter one at a time, their entrances are described as "staggered".  Other suggestions for the same event are development, canon and Mannheim Crescendo. Many believe there is no exact term.
It is possible that there is no accepted term for this, but some suggestions include "development", "canon" or "Mannheim Crescendo".