prolongation

n. extension, making longer, act of lengthening

In music, especially Schenkerian analysis, a prolongation creates the detail of a musical composition by elaborating the background structure. Prolongations include diminutions. A coda is a passage which brings a movement or piece to a conclusion through prolongation.
See more at Wikipedia.org...

Noun
1. the act of prolonging something; "there was an indefinite prolongation of the peace talks"
(synonym) protraction, perpetuation, lengthening
(hypernym) continuance, continuation
(derivation) prolong, sustain, keep up
2. amount or degree or range to which something extends; "the wire has an extension of 50 feet"
(synonym) extension, lengthiness
(hypernym) longness
(derivation) prolong, protract, extend, draw out
3. the consequence of being lengthened in duration
(synonym) lengthiness, continuation, protraction
(hypernym) duration, length
(derivation) prolong, sustain, keep up

n. prolongation, extension, protraction; overtime, stretching

(n.)
The act of lengthening in space or in time; extension; protraction.
  

(n.)
That which forms an additional length.