I have been playing this song for a long time. It may be one of the top 10 perfect pop songs of any music period.
Interestingly, Diamond — who recorded a version of the song for his 1967 album Just for You — considered “I’m a Believer” to be a country song when he wrote it; he envisioned country music star Eddy Arnold recording it.
“I thought it would be a great song for him,” Diamond noted. Music executive Don Kirshner, who knew Diamond from New York’s Tin Pan Alley and was working with the Monkees’ TV producers, steered it to the group instead.
Read the whole thing at source:
https://www.guitarplayer.com/music/neil-diamond-on-the-monkees-hit-im-a-believer