Expansion: the unhurried growth of an idea across avartans — lengthening phrases, thickening subdivision, opening new corners of the material while the source stays recognizable. It is the pacing principle behind peshkar and kaida development alike.
Vistar is judged by proportion. Growth that leaps ahead exhausts the material early; growth withheld too long loses the listener. The traditional counsel is that each variation should sound implied by the one before it.