After becoming a staff engineer at Larrabee Sound in West Hollywood, she was hired by Zoo Records/BMG to produce Green Jellö's major label debut album,[11] which featured members of a new Los Angeles group called Tool.
[10] In Los Angeles, Massy was an engineer, producer or mixer on recordings from artists including Aerosmith, Babyface, Big Daddy Kane, Bobby Brown, Prince,[13] Julio Iglesias, Seal, Skunk Anansie,[14] Paula Abdul, Ryuichi Sakamoto and many more.
With Rubin, she also recorded Tom Petty and the Heartbreakers, Slayer, Donovan, Geto Boys, the Black Crowes, Danzig, and System of a Down's debut album.
[18] In the '90s, Massy produced material for Red Hot Chili Peppers, Sevendust, and Powerman 5000, which featured guest appearances from Rob Zombie[19] and actor Malachi Throne; and for newcomer Pauley Perrette.
She acquired the theater property in 2001 in Weed, California, and operated it as a recording studio for 11 years, with notable clients having been Sublime, Dishwalla, Swirl 360, Econoline Crush, Cog, Spiderbait, Norma Jean, Built To Spill and From First To Last (featuring Sonny Moore of Skrillex.
In the 2000s, she wrote a regular column in Mix Magazine called "Gear Stories"[24] which discussed vintage recording equipment versus modern equivalents.
She has presented periodic recording workshops in Dresden at Castle Rohrsdorf and at Mix with the Masters in Les Studios de la Fabrique in Saint-Remy-de-Provence in the south of France.
[29] In 2016 Massy recorded Seattle all-woman noise band Thunderpussy in an abandoned nuclear power plant's cooling tower for the song "Torpedo Love".
She also produced albums by Econoline Crush, Far From Alaska and Dishwalla, and was hired to re-work the recordings of Grey Daze, a side project by Linkin Park's frontman Chester Bennington.
In early 2018, Massy traveled to Mexico City to produce the MTV Unplugged television broadcast (and subsequent album release) of the band Molotov.
In the summer of 2018 she gained access to the abandoned London Underground station at Aldwych to record British band God Damn on the subway platform.
The album features performances by Dave Grohl (Foo Fighters, Nirvana), Joe Walsh (Eagles), Chrissie Hynde (Pretenders), LeAnn Rimes, Nancy Wilson (Heart), Perry Farrell (Jane's Addiction, Porno For Pyros), Roger Taylor (Queen), Chris Chaney (Porno For Pyros) and Duff (Guns N' Roses).