On May 1, 2007, an e-mail sent to those on the Beastie Boys' mailing list revealed the album is all instrumental.
OK, here's our blurb about our new album — it spits hot fire! — hot shit! it's official... it's named THE MIX-UP. g'wan. all instrumental record. "see i knew they were gonna do that!" that's a quote from you. check the track listing and cover below. you love us. don't you?"
On June 21, 2007, a legal stream of the entire album was released on BrooklynVegan.com. Drummer Mike D said that "even though The Mix-Up is a 'post-punk instrumental' album, the Beasties have no plans to ditch vocals for good. In fact, they are currently planning another version of the album that will feature collaborations with 'a pretty wide array' of 'mostly newer' vocalists." Two singers speculated to be featured on the vocal version were Jarvis Cocker and M.I.A..
In an interview with The Aquarian Weekly, published in February 2008, the band was asked if they were making a statement about the status of hip-hop music by releasing an album strictly of instrumentals. “In a way, the album was a reaction to our hip hop," said Ad-Rock "Our last record was an all rap record, so when we started recording [The Mix Up] we wanted to work with some instruments, and it just sounded cool, so we kept with it.”  Mike D expanded on Ad-Rock's response, adding, "We get asked, ‘What do you think of the state of hip hop today?’ a lot. Maybe I’m being defensive, but it seems like people always look for us to come out and criticize hip hop. But hip hop is what we grew up on, and it continues to be one of the only forms of music left that strives on evolution and innovation. Yeah, we might be in a spell where we’re waiting for that next record to come out and change everything—but still, that’s what hip hop is and that’s what puts it in its unique place.” 
The album debuted at number 15 on the U.S. Billboard 200, selling 44,000 copies in its first week. It is their lowest charting album in the US so far, the highest being Hello Nasty, which debuted at number one.Uncut magazine gave it four stars out of five, saying "The Mix-Up is the best record collection ever thoroughly digested and re-imagined by a bunch of guys in love with sound."The Mix-Up won a Grammy in the Best Pop Instrumental category.