Silbido

is a technique used by the Arrancar, Findorr Calius.

Description
By blowing upon either of the knife-like protrusions at the end of his sleeves, Findorr can emit a high-pitched whistling sound. In doing so, he is able to call forth, from a different space to his own, a hoard of Gillian-class Hollows to the locations of his choosing.