Yass (jass) is a Polish music style of avant-garde jazz which originated in the late 1980s, that mixes jazz, improvised music, punk rock, and folk.
The style began with avant-garde jazz musicians from the Tricity and Bydgoszcz, where the jazz club Mózg became the unofficial 'home venue' for Yass performers, with its own label releasing a number of Yass productions.
The first Yass album is generally regarded to be Tańce bydgoskie by Trytony.
The most seminal period for Yass was in the 1990s, with many active groups performing and releasing albums, including Miłość, Łoskot, Trytony, and Mazzoll & Arhythmic Perfection.
released by Jazz Forum magazine shortly after the genre's heyday.