Actually, Wilson's approach to music, especially during the peak of his creative powers in 1966-71 (Pet Sounds thru Surf's Up), was to create short pieces of melody (which he called "feels") and assemble them together into larger pieces, especially as in "Good Vibrations" and "Heroes and Villains". The longer version of the latter (as on the SMILE album) contains sections known to Beach Boy fans as "Bicycle Rider", the "Cantina" section, "Plymouth Rock" and "Grand Coulee" and there are other bits such as "Child is Father to the Man", that wound up in both "Cool, Cool Water" and "Surf's Up".
Many of these original bits as recorded by the Beach Boys in 1966-67 can be heard on the CD release of Smiley Smile / Wild Honey and on the Box set Good Vibrations - 30 Years of The Beach Boys. Leonard Bernstein was an admirer of Wilson's writing and arranging skills and included the song "Surf's Up" as a work in progress by Wilson on a circa 1967 TV special.