March 06 1967 was a busy day at EMI Studio 2 for the Beatles. The overdubbing of french horns for the title track of the newly decided title being: "Sgt. Pepper's Lonely Hearts Club Band".
The horns were mainly added to the chorus of the song as well as the ending whereby they would hold a note while the backing continued. At this point there was no fade out and the bass line and drums continued and then simply stopped once the length of the ending was accomplished.
Once the horns were recorded, George Harrison added his stinging lead guitar to the proceedings and put on the same track as the horns (track 3). Finally, audience ambiance and noise was added to the mix on track four with some laughing and chatting and applause - added to track 4. There was also at the very beginning of the song before the music started whereby the orchestra was warming up and tuning along with some chatting. As stated, the chatting was taken from a library tape whereby the orchestra tune up was taken from the February session of "A Day In The Life" where the orchestra was present for the orgasmic overdub. The isolated crowd noises can be heard on the CD bootleg "The Lost Pepperland Reel".
Three attempts at a mono mix was completed at this session as well as eight attempts at a stereo mix. There are differences in both mixes with the audience noises and the fact that the lead guitar/audience is much louder in the mono mix. The commercial stereo mix has Paul's vocal isolated in one speaker and moving across the stereo spectrum with the group vocals also isolated in the other speaker and also moving around the spectrum. This was changed on the Apple/EMI CD/LP "Yellow Submarine Songtrack" where the vocals were centered and the group vocals were separated on each speaker during the chorus. There is also a breakdown of the title song available on bootleg.