jam session

Translations
музыкальная импровизация
They had a jam session at his place last night.
Они устроили музыкальную импровизацию у него дома вчера вечером.
Definitions
An informal gathering of musicians who play improvised or unrehearsed music together, often to experiment, practice, or enjoy making music collaboratively.
Words
jam

noun
джем
session

noun
сессия