Nate Mercereau shares a new track, “Facing The Sideways Rain,” featuring Kamasi Washington and Carlos Niño. Mercereau’s friendship with Niño also recently led to him playing on six of the tracks on André 3000’s surprise new album, New Blue Sun. Mercereau offers more context:Kamasi, Carlos and I have only had one short recording session as a trio, but it yielded a …