While attending Laguna Beach High School, he fell in with a handful of like-minded music fans and formed a band that played local parties. Cronin left California for a few years to attend Lewis & Clark College in Portland, Oregon, but returned to continue his education at the California Institute of the Arts. While attending CIA, he joined the surf-influenced garage band Charlie & the Moonhearts as bassist; they became simply the Moonhearts after the departure of drummer Charlie Moothart, and in 2010 the band released a self-titled album through Tic Tac Totally Records. Cronin also began collaborating regularly with Ty Segall, releasing a collaborative album, Reverse Shark Attack, in 2009 and playing in Segall's road band.

According to Cronin, his first solo album began as therapy after finally completing college and making his way into the real world; full of noisy pop and garage influences, the self-titled LP (featuring guest appearances by Segall, Moothart, and John Dwyer of Thee Oh Sees) was issued by Trouble in Mind Records in September 2011. While still playing with Segall, he released a second solo album, MCII, for Merge in the spring of 2013. He embarked on a solo tour after that, taking time during 2014 to write and record his third album. Adding some new instruments to the fold, including the traditional Greek instrument the tzouras, and making a concerted effort to make his sound "bigger," the album was split into halves, with one side straight-ahead pop songs and the other a thematically linked set of songs meant to tell Cronin's coming of age story. The record, titled MCIII, was released by Merge in the spring of 2015. ~ Mark Deming