At the age of 14, after attending a KISS concert, Friedman took up the guitar, and is largely self-taught. He rushed to form a band and started playing original songs, the reason being that originals are easier to play than covers. “Because,” he says, “even if you screw up, you just claim that the song is written like that and no one can challenge you.” The mother of one of Friedman’s friends ran an event center with a two-level stage, and Friedman and his friends used it as a rehearsal space. Soon word spread about their band, and, since they were in a rural area, people would come from miles around to socialize and listen to music. “Rehearsals” very quickly became live shows. Friedman formed and played lead guitar in several other bands, including Deuce, Hawaii (which had previously been called Vixen), and notably Cacophony. Cacophony featured neoclassical metal elements and synchronized twin guitar harmonies and counterpoints shared with guitarist Jason Becker. He played guitar on the 1987 album It Won’t Be Long by Christian rock band Shout. In 1988, he recorded demos for Jet Red that eventually were released as bonus tracks on the 2009 Jet Red release “Flight Plan”. In August 1988, he released his first solo album, Dragon’s Kiss.

When Cacophony disbanded in 1989, Friedman auditioned for the thrash metal band Megadeth after a tip from his friend Bob Nalbandian, Friedman officially joined Megadeth in February 1990. Friedman’s audition can be seen on the Megadeth DVD Arsenal of Megadeth. The first album he recorded with them was Rust in Peace which was released on September 24, 1990. Rust in Peace was certified platinum by the RIAA in 1994 and was nominated for the Best Metal Performance Grammy at the 33rd Grammy Awards.

Friedman further developed his style of playing exotic scale solos from the Cacophony era, and integrated it into the music of Megadeth. In July 1992, Megadeth released Countdown to Extinction, which was a more commercial album, aimed at a wider audience, and sold double platinum. Friedman played on Megadeth’s further releases Youthanasia (1994), Cryptic Writings (1997), and Risk (1999). After a total of five studio albums with Megadeth, in December 1999 Friedman announced his departure from Megadeth. His last show with them was on January 14, 2000. Friedman later stated that he got tired of “holding the flag” for traditional metal and felt that he could not evolve as a musician. In an interview with Ultimate-Guitar.com in March 2007, Friedman claimed that he wanted Megadeth to move towards a more aggressive sound and that he’d rather have been playing straight pop music than the pop-influenced metal Megadeth was playing at the time. During Friedman’s time in the band, they sold over ten million albums worldwide.

Friedman appears on Japanese television and is also a contributing columnist to Japanese music magazines and national newspapers. Speaking Japanese, he became a regular member of the cast of TXN’s musical TV program Hebimeta-san (ヘビメタさん) (anglicized as “Mr. Heavy-Metal”) with Japanese idol Yoko Kumada until the show came to an end in 2005. Friedman had his own heavy metal TV program called Rock Fujiyama alongside Shelly, Ken Ayugai (Kenny Guy), Yorimasa Hisatake (Rock Ninja Yorimasa) and ex-Scanch member Rolly Teranishi from April 2006 until March 2007. From November till December 2005, he toured with singer Ami Suzuki on her “Suzuki Ami Around the World” live house tour, which took place in Tokyo, Osaka and Nagoya. Friedman was featured on Jukebox, a television program in which Friedman and two Japanese people translate the lyrics of various English songs into understandable Japanese. He has also made guest appearances on the television programs Eigo de Shabera Night and Tamori Club. In 2008, Friedman played the role of Paul Weinberg, an English language teacher, in Isshin Inudou’s Gou-Gou Datte Neko de Aru.

In 2009, Friedman collaborated with Ema Gelotte and Tinna Karlsdotter from “All Ends” as the lead guitarist for the song “With Me” which was featured in the game, Sonic and the Black Knight. In 2010, Friedman launched a record label under Avex Group, called Gokukara Records. In February 2010, during C. J. Ramone’s Japan tour, he made a guest appearance on guitar for “California Sun”, a cover song previously released by The Ramones on their 1977 album, Leave Home.

In 2009, Friedman appeared on The Quiz Show, a Japanese TV drama starring Sho Sakurai as a guest professor. On January 4, 2014, Friedman took part in New Japan Pro Wrestling’s Wrestle Kingdom 8 in Tokyo Dome event, playing Hiroshi Tanahashi to the arena.

In 2011, Friedman collaborated with Japanese idol group Momoiro Clover Z, providing guitar for their song “Mōretsu Uchū Kōkyōkyoku Dai 7 Gakushō “Mugen no Ai””, which would become a hit in 2012.

In 2011, Friedman also worked with Ayanocozey Show to make the song SAMURAI STRONG STYLE, theme of the Tokusatsu movie Kamen Rider × Kamen Rider Fourze & OOO: Movie War Mega Max The catchphrase for the movie is “In Winter 2011, Movie War Will Evolve” (2011年冬、MOVIE大戦が〈進化〉する, Nisenjūichinen Fuyu, Mūbī Taisen ga Shinka Suru). Friedman and Ayanocozey had previously worked together when they joined the Japanese promotional super-group FANTA, releasing the 2010 single “Fantastic Love”. Friedman stood for the “F” in FANTA, Ayanocozey stood for the first “A”, and the other members of the group made up the other letters.

In December 2012, Friedman married Japanese cellist Hiyori Okuda in Yokohama, Japan.

In 2013, Friedman released his first library of guitar loops on LoopArtists. Friedman recorded collections of clean-tone, high gain lead and rhythm guitar loops that are intended for use in a production and remix environment. Friedman has been doing concert tours for the Bravely Default original soundtrack in 2013 as well as the Budokan concert tours among others. In combination with these tours he has also released his new album Inferno in 2014 which he is now touring across Europe going to places such as Norway, Poland, Netherlands and Germany.

In 2014, Friedman collaborated again with Momoiro Clover Z, providing the guitar track for their single “Moon Pride”. The song was also used as the opening theme music for the television series Sailor Moon Crystal, which premiered in July that year.

In 2018, he collaborated with MAN WITH A MISSION’s Jean-Ken Johnny, KenKen, and Kōji Fujimoto for the song “The Perfect World” which was used as main theme for Netflix Original anime series B: The Beginning.