from Toras Aba
"There are places (Oberland & Germany) where the Minhag was for the Chazan who
Davens Ma'ariv on Motzei Shabbos Selichos to sing the Vehu Rachum with a special Niggun.
The Imrei Pinchos says it is called "The long Vehu Rachum" based on the Sod of אריך אנפין
(long face) Kabalistic term for Hashem being patient with us and giving us more time to do
Source: Andrew Schwartz