Within the album, there are songs that resonate with a longing for escape, such as When the Swallows Fly or I've Decided to Join the Air Force, the latter inspired by a performance alongside the Royal Air Force at the Royal Albert Hall. In the Summer of His Years, on the other hand, was a tribute by Robin Gibb to Brian Epstein, the manager of the Beatles, who passed away in 1967. Tracks like I've Gotta Get a Message to You and I Started a Joke became important singles, although their availability varied between the UK and North America. In some editions, Such a Shame, written by Vince Melouney and which spoke of the group's disintegration, was replaced by I've Gotta Get a Message to You.
The recording process for Idea began shortly after the sessions for the previous album, Horizontal, and extended throughout the early months of 1968, with a break for the Christmas holidays in Australia. During this period, the various tracks took shape, some recorded in January, others in February, and work continued until June and July. There was even a side project in June where Robin recorded seven solo songs. The album, with a total running time of just over 35 minutes, was released in mono and stereo formats, and later, in 1989, was reissued on CD including tracks that had been excluded from some original versions.