Hiro Yamamoto was with Chris Cornell in the band The Shemps during the early 80's. Yamamoto left for a hile and was replaced by Kim Thayil. But he kept contact with Cornell. After The Shemps broke up, the two started jamming again. After Soundgarden formed, Yamamoto helped with Soundgarden's first five albums/EP's. After getting into an argument at the Melkweg in Amsterdam, Yamamoto left. He had been with Soundgarden until 1989.
In 1991, Yamamoto formed the independent band Truly with drummed Mike Pickeler from the band Screaming Trees and vocalist Robert Roth from The Storybook Krooks. The band focused on bringing a psychedelic sound to grunge, similarly to Screaming Trees and Love Battery.