Frequency Unknown is a studio album released under the name Queensrÿche; it was released by Geoff Tate's temporary version of the band, before a settlement determined that only the other band members were entitled to use the name Queensrÿche. The album was released on Cleopatra Records' sub label, Deadline Music, on April 23, 2013, as music download, on CD and limited edition vinyl LP in the United States and on May 21, 2013, as audio cassette which excludes the re-recorded classics, and on June 3, 2013, on CD in the United Kingdom.

It was co-written, and originally produced and mixed by Jason Slater, who has previously also produced Queensrÿche's albums Operation: Mindcrime II (2006), American Soldier (2009) and Dedicated to Chaos (2011). Frequency Unknown is Queensrÿche's last album to be produced by Slater, and was the final album he produced prior to his death in 2020.

It was revealed to the public on April 28, 2014, that Geoff Tate lost the rights to the Queensrÿche trademark. After the settlement was announced, Tate changed the name of his version of Queensrÿche to Operation: Mindcrime.

Background Queensrÿche's twelfth album, Dedicated to Chaos, was released in 2011 to a mixed reception, with some critics giving positive reviews, and others panning the album due to great stylistic differences to previous albums.

Furthermore, it became apparent that there were tensions between lead vocalist Geoff Tate and the rest of the band. These tensions openly manifested themselves at a concert on April 14, 2012, in São Paulo, Brazil, when Tate, who was irate over the firing of his wife and stepdaughter as the band's manager and fanclub manager, respectively, allegedly physically assaulted and spat on drummer Scott Rockenfield and guitarist Michael Wilton. After hoping to reconcile with Tate, the other founding members Rockenfield, Wilton and bassist Eddie Jackson decided to fire him. (Exhibit E.) Meanwhile, Jackson, Rockenfield, Wilton and guitarist Parker Lundgren had been working with another vocalist, Todd La Torre, under the name "Rising West", playing material from the first five Queensrÿche albums. Following Tate's expulsion, La Torre was officially announced as Tate's replacement.

Tate subsequently filed a preliminary injunction lawsuit, disputing ownership of the band name, that resulted in a verdict that both Tate and the other band members were allowed to use the band name until the next court date, scheduled for November 2013. Tate subsequently started his own version of the band featuring former Queensrÿche guitarist and producer Kelly Gray, guitarist Glen Drover (Eidolon, King Diamond, Megadeth), bassist Rudy Sarzo (Blue Öyster Cult, Ozzy Osbourne, Quiet Riot, Whitesnake), drummer Bobby Blotzer (Ratt) and keyboardist Randy Gane. Drover was later replaced by Robert Sarzo, and Blotzer with Simon Wright (AC/DC, Dio).Glen Drover Quits Geoff Tate's Queensrÿche. Blabbermouth.net. Retrieved on 2012-11-26. Tate's band went on an "Operation: Mindcrime Anniversary Tour",Geoff Tate: Heading to the Future with a New Queensrÿche. Entertaim.net. Retrieved on 2012-11-26. and lost the name Queensrÿche to the other remaining band members in April 2014.

Title and artwork The title, release date, track listing and artwork of the album were announced on March 4, 2013, a few hours after the original Queensrÿche, with Todd La Torre on vocals, announced the release date of their album, Queensrÿche. A press release states that "F.U. might be perceived as a fitting tribute and salutation", and later clarifies: "Coincidental abbreviation? Unlikely." The abbreviation "F.U." is further emphasized on the album artwork. The letters are often used in English as a euphemism for the profane expression "fuck you". Todd La Torre, the frontman of Queensrÿche in Tate's place, feels that the artwork is "below the belt" and said that subliminal insults are "not what Queensrÿche was about", further emphasizing by saying "when one talks about devaluing the name or the brand of Queensrÿche, it's so obvious that when you're putting a fist with an 'FU' in a clever way to say that's Frequency Unknown, but we know what it's really likely to be standing for, (...) that doesn't add credibility or respect to the name and brand of Queensrÿche."

However, when Tate was asked how he came up with the title Frequency Unknown and whether the FU or the Frequency Unknown? came first, he said: "I’ve been trying to come up with an answer for that because I knew I would be asked. I haven’t really come up with one yet." When Eddie Trunk inquired about the F.U. initials being aimed towards his former bandmates, Tate responded: "Oh gosh, people read so much into everything. It's kind of funny, isn't it?"

In later interviews, Tate did explain the title. In May 2013, he said: "When you are making music and you are putting a song together you have all these different parts that are supposed to work together. Sometimes when you are listening back to it something’s doesn’t click. There is a theory in the engineering world if you dial in these unknown frequencies nobodies knows what it is you find the weak spot of the song. It kind of gels together and all of a sudden it is now great. Like there it is it all comes together because I dialed in this frequency. But no one can tell you what this frequency is. It is an unknown thing. That became a little studio phrase that got thrown around while we were working on the project and that became the title of the record." Later, he called it... "...this certain frequency of equalization that brings all the notes and the whole mix together; it becomes incredibly focused at that point. It’s this unknown frequency that you’re always looking for, and nobody knows what it is. You just start fiddling with the dials until it sounds good to everybody."

The fist on the album cover would originally be Tate's own fist, but a different hand model was used because Tate wanted a more masculine-looking fist with hair on the knuckles.

Songs The album includes ten original songs and four bonus tracks. The song "Give It to You" appeared on an earlier track listing as "When Lightning Strikes". The bonus tracks are re-recordings of four of Queensrÿche's greatest hits. Tate said that he was motivated to re-make the four hits due to the money they would earn by doing so. He also said "They wanted them to sound, you know, as close as we could make them to the originals. And that's what was really hard, was making them sound that way." Tate initially wanted to do re-interpretations of the songs with different arrangements, but Cleopatra Records allegedly did not allow this.

"Cold" was released on March 3, 2013, via iTunes as the first single off Frequency Unknown. It was also released as a special limited-edition 7" vinyl single with the re-recorded version of "Silent Lucidity" on the B-side. On April 15, 2013, Cleopatra Records made the entire album available for streaming on SoundCloud, but these were removed by midnight. Ultimate Guitar Archive asserts that the predominantly negative reactions to the recordings may have prompted the label to pull the album stream.

Subject matter in the album's lyrics include: Relationships ("Cold", "Life Without You" and "Everything") Standing up for oneself ("Dare") The idea that everyone is a slave ("Slave") The mindset of a terrorist ("In the Hands of God"), Dealing with rape and violence ("Running Backwards") Addiction ("Fallen") Mortality ("The Weight of the World") Also, Geoff Tate has described "Give It To You" as a "jam song".

Randy Gane wrote "The Weight of the World" in response to suffering a heart attack on December 26, 2012, explaining: "that was a very difficult piece to produce and to arrange, 'cause I was going through some recouping and that song was quite autobiographical for me."

Rockenfield, the drummer of Queensrÿche, said in May that he had heard several parts of the album, saying that it was "quite professionally made, but it has got virtually nothing to do with what once distinguished Queensrÿche(...)It is rather bitter if Geoff seriously believes that these [re]recordings [of the four classics] tap into the heart of these pieces."

Writing and recording Frequency Unknown was recorded at the A&D Studios in Sunnyvale, CA and was created in the short time-span of six weeks, which Tate explains was due to: "[wanting] to get it done to coincide with the tour dates, you know, and have an album and a tour at the same time." Tate said that the writing process "started out with a group of core writers, and we wrote a bunch of songs, and then we had invites out to a lot of different people to play on it. (...) We started writing it in January and finished it March 1st." This writing team was composed of four members: Tate, Slater, Lukas Rossi and Gane; additionally Martín Irigoyen and Chris Cox were credited. Tate had met Rossi during the Shiprocked tour of 2012: "We were having a couple of drinks talking music and the next thing I know we're back at the hotel writing songs."

The album has many in-studio guest appearances by musicians outside of Geoff Tate's version of Queensrÿche. According to Tate, “the idea of having guest appearances evolved from the time constraints we had imposed on the project.” Later, he did comment that "[it] was really fun... from an artistic standpoint. [But] from a logistic standpoint, it's like a nightmare," due to scheduling these musicians. Guitar solos from musicians outside of the band and production team were contributed by K. K. Downing, Chris Poland, Ty Tabor, Brad Gillis, Dave Meniketti and Chris Cannella. These musicians were brought into the studio on the same day and at the same time, except for K.K. Downing, who was in England and sent his materai to Tate via the internet.

Nina Noir sung backing vocals on the re-recorded version of "Jet City Woman". Tate's daughter Emily and stepdaughter Miranda sang backing vocals on the re-recorded version of "Silent Lucidity". Articles on Blabbermouth.net also named Lita Ford as a guest musician on the album, but she was not credited, nor was she officially announced.

Outside of the guest appearances, the album predominantly makes use of session musicians rather than the official members of the band. The guitars, bass and drums on all four re-recordings were performed by Martín Irigoyen. Craig Locicero plays the rhythm guitar tracks on all ten original tracks; Paul Bostaph and Evan Bautista each played drums on four tracks, and Slater played bass on six tracks, keyboards on two tracks, and performed a theremin solo on one track. Of the official members, Tate sang vocals on all tracks; Randy Gane performed keyboards on six tracks, bass on one track, and provided the orchestration for one re-recording; Rudy Sarzo played bass on three tracks; Simon Wright performed drums on two tracks, and Kelly Gray and Robert Sarzo each played a guitar solo on one track.

Mixing