Mono Masters is a compilation album by the Beatles, and is an alternate, all-mono version of the album Past Masters. Those mono mixes were THE mixes the producer and the band worked on when the albums were originally recorded and released in the UK.

Until one day, a schoolmate invited me to his house and made me listen to his father's mono equipment. An unknown quantity of unnumbered red boxes (sometimes reported to be between 300 and 500) were issued in the UK, while 1000 numbered black boxed sets were assembled and issued in the United States by the Dutch East India Trading Co. A new Mono Box, containing remastered monoural versions of the Beatles' core albums (with the exception of Yellow Submarine album) plus Mono Masters compilation, was released on 9 September 2009 along with Stereo Box and new stereo reissues of the individual albums, including the first four albums given their stereo debuts on CD. I now noticed that it was in fake pseudo-stereo, which I don't think I even noticed when I first got it.

Stereo recordings were a fairly new concept for pop music in the 1960s and did not become standard until nearly the end of that decade. When you're listening to music being played, live, in front of you, the singer's voice isn't only coming out of the right speaker. My opinion is they should not have tried to make them stereo in the first place as it did not work well at all. Surround sound is a real thing and so is spatial audio, that's true, but stereo is still the dominant format.

It's nice when you play a track, the music envelops you, and you can place the elements of the track on a virtual stage all by ear. I listened to it very little when I first got it and for years afterwards, but the Lewisohn book piqued my interest in re-listening to it.A Karlson speaker and a monophonic amplifier revealed to me the sonic difference that exists between a wide frequency spectrum and a good acoustic cabinet or two channels with small speakers. As a result, the track listing for Mono Masters differs from Past Masters on the second half of disc two, omitting some later songs that never had a mono mix ("Old Brown Shoe", "The Ballad of John and Yoko" and "Let It Be"), and adding several songs released on stereo-only albums that had unreleased mono mixes. Of course, the bigger version with the records is more desirable but this is pretty good alternative too :).