A leading saxophonist on the Japanese improvised music scene, Junji Hirose also gives performances using self-made analog noise instruments. It was in the 1980s that Hirose started presenting noise performances on his SSI (self-made sound instrument), made of various everyday objects. Over the years he continually modified the instrument, for each version attaching a different number to the name SSI. On the Hitorri label, Hirose has released the CDs "SSI-4" (hitorri-997 / 2013), "SSI-5" (hitorri-993 / 2015), "SSI-6" (hitorri-990 / 2016) and "SSI-7" (hitorri-979 / 2020).

Around 2021, Hirose started presenting SSI performances as a series at the Tokyo event space Pool, holding several of these concerts a year. "DUO-1," a duo CD by Hirose and Otomo Yoshihide (ftarri-965 / 2022), documents a performance at a concert in this series. In May 2024 the series was temporarily suspended, and on July 13 and October 6 of that year Hirose recorded SSI performances with no audience at Pool to document the results achieved in the series. This CD contains five pieces from those recordings.

The pieces on tracks 1 to 4 were performed using the SSI-4--track 1, with a type that includes two bicycle wheels, and tracks 2-4, with a type that has two large metal trays attached. The performance on track 5 does not use the SSI; instead, air compressors were used to direct powerful condensed air onto microphones, producing explosive sound. Colorful sound, white noise, soft sound, explosive sound--noise with a different feeling is created in each of these performances.