Josh is a classically trained pianist, composer and producer. Josh's indie-pop project MOUNTNS was created in 2016 with the release of "Hey Love", a collaboration between Josh and Lewis Lane (EAR MILK premiere).

As a composer, Josh has worked on various commercial and narrative projects. Josh composed the original score to "Swedish Auto" featuring January Jones and Lukas Haas. "Out of this comes a very patient, very confident revelation of character and background, buoyed by the evocative music of Josh Robertson and expert sound editing of Ahmad Shirazi." (Variety Review).