Amandistan... IMO, those songs weren't supposed to have 'depth'. They were just silly pop songs from a bunch of young lads... and perfect ones at that. The concept of 'pop music' has been so degraded in recent decades, drowned in hype, fashion and bad imagery... sometimes, all that is needed is a simple concept and simple instrumentation. And the likes of IWHYH is just a perfect example...

The Perfect answer Master Ray. They were pop songs in the mid 60's all theses songs were on AM Radio so the length of the music was not supposed to go over 3 minutes.
Let me say as an American growing up in that time You may not realized just what the Beatles did. Popular music that time was very different for one music radio there was color barrier. Some stations did not play music by black artist That was policy in some places the top acts at least around the time just before the Beatles crossed the Pond consisted of the remains of the Doo Wop Groups. Of course Bill Haley, Chuck Berry, of course Elvis was the King and probably Franki Valli & the 4 seasons The sound coming out of Cali was surf music with the Beach Boys and Jan & Dean for the blacks Chubby Checker and the Motown sound was our staple with the exceptions of a few TV variety shows most of those acts Never played together in shows Read up on the Chilitin Circuit that Black Acts had to go on some real good stories.
The Beatles changed all that in one show on Ed Sullivan. Because of the Beatles they helped every other band in England as the changed in the sound of the music and the thirst of American audiences for something new every band that was from England came and made the Sound of Rock & Roll change. from the Stones the Kinks, Freddy & The Dreamers, Hermans Hermits, The Who, The Animals, The Yardbyrds, The Zombies, All these bands can thank the Beatles for expanding and changing the music The 1st British Invasion I am a witness to it I saw and grew up in it.
Not only that but it made American acts travel over to Europe and the stories I heard from the Black musicians who toured Europe and how warmly they were greeted and the huge audiences they had at their shows most of them never played before white audiences before It was because of the Beatles and the other British Acts who grew up on Chuck Berry or Fats Domino, Miles Davis, Muddy Waters, BB King and said that they got their inspiration by these Black music acts.soon some Radio stations started to play both Black and white music in their setlist that's how FM came into being the place to hear all this great music.
