Before Pet Sounds The Beach Boys were looked at as a mainly commercial pop group that was talented but that's what they were mainly known as. Their previous work was more focused on the California surf and youth lifestyle. With Pet Sounds they expanded their musical output instead of it sounded like another 'Surfin' USA' it had a wider berth.
Instead of a more commercial sound, which was popular at the time, the lyrics were more experimental like 'I Know There's an Answer' which was written while Wilson was taking acid. The change of the sound was mainly because of Brian Wilson who was a member of the band he was the main writer and producer he had stopped touring to work on producing and writing more music. The result was Pet Sounds which contained more complex lyrics and less fillers, The Beatles 'Rubber Soul' was a huge inspiration for him it led him to push himself musically and test the boundaries. He also took from Phil Spector and his 'Wall Of Sound' technique and created a dense sound by layering the instruments on top of another. He was one of the few who used the 'studio as an instrument'.
One of the major differences was that he used different items as instruments like bicycle bells and Coca-Cola cans and expanded the harmonies more elaborately. His elaborate tracks were made usually with his session players 'The Wrecking Crew'. I am not really a huge fan of the Beach Boys but I really do like this album.
I enjoy the harmonies that are in there especially the instrumental track, 'Let's Go Away For Awhile' it honestly didn't need words and was a beautiful track. As someone who loves music and innovation I love when artists and producers push the boundaries and change the format, this album left it's mark on pop music.