In 1968, Yellow Submarine was released and The Beatles wanted an album to go with it, so they decided to go with a mono EP consisting of "Only A Northern Song", "Hey Bulldog", "Across The Universe" (which wasn't in the movie), "All Together Now", and "It's All Too Much". However, the EP was scrapped and the album we know was released instead and was the only full length album with original tracks released in the UK during The Beatles lifetime that did not make it to #1 in the UK (A Collection Of Beatles Oldies and Magical Mystery Tour failed to reach this too, but ACOBO was a compilation album and MMT was a double EP until 1976) and also the only UK album to feature songs half Beatles songs and half orchestral songs by George Martin (though A Hard Day's Night and Help! had these orchestral tracks too, this was only in America. Also, George plays sitar on Sea Of Time, which technically means that The Beatles are on both sides).
All five of these songs can be found in their original state on Mono Masters.