Good Day Sunshine is a song written mainly by Paul McCartney for the Revolver album. In his authorized biography, McCartney explains that it was a conscious attempt to emulate the Lovin Spoonful’s Daydream. This was one of a number of feelgood Summer-themed hits at the time, and Paul fleshed out the idea while driving to Lennon’s house for a songwriting session, as he recounts in The Lyrics:
I’d driven myself there from my home in London in my beautiful sierra-blue Aston Martin, ejector seat and all. I love to drive, and an hour’s drive is a good time to think of things; if you’ve got half an idea, you can flesh it out on the way. I would often arrive at John’s place with a fully formed idea.
Around that time there was quite a spate of summer songs. ‘Daydream’ and ‘Summer In The City’ by The Lovin’ Spoonful, The Kinks’ ‘Sunny Afternoon’ – I think all those came out during the same year, 1966. We wanted to write something sunny.
It was now time for us to do ours. So we’ve got love and sun, what more do we want? It’s really a very happy song.
Indeed it is an extremely upbeat positive number, with a very simple short lyric, and not a trace of doubt or uncertainty let alone sadness. The music is similarly upbeat with not a minor chord in sight, although it is less simple than it might appear: the timing of the chorus is irregular (in my transcription there are several time signature changes, although it can be seen as a slow syncopation) and there is also, effectively, a key change between verse and chorus. Although very upbeat songs can feel trite or simplistic, they are not easy to write! McCartney is deeply committed to creating a positive impression and he believes that love, happiness, contentment are nothing to be ashamed of: “I feel good in a special way”, “I’m so proud to know that she is mine”. Good Day Sunshine expresses contentment and happiness very clearly and in this sense it succeeds. It probably feels pretty uplifting to sing. whether those feelings are evoked in the listener is a slightly different question.
Capturing the mood of the gloriously hot summer of 1966, ‘Good Day Sunshine’ kicked off side two of Revolver.

Perhaps it’s a very personal response, but I think happy songs can sometimes feel a bit unfulfilling for the listener (after all the singer is having a good time, but are we?). I think this is because contentment is a target or destination. If the function of music is to move the audience, then it is about the journey rather than the destination. It’s not that I don’t get positive emotions from music, but when I do I think of examples like I Got A Feeling (Black Eyed Peas), Crazy In Love (Beyoncé), Cloudbusting (Kate Bush) and I think what these have in common is that they are as much about excitement for the future as they are about contentment in the present. As Kate Bush puts it: “I just know that something good is gonna happen.” For this reason, I am unlikely to pick out Good Day Sunshine to listen to in isolation, but I do like it in the context of the album, where it helps to balance the emotional tone against bleaker songs dealing – literally – with loneliness, death and taxes. Revolver strikes this balance pretty nicely, although the individual tracks are very varied – the most emotionally varied of any Beatles album, I think. Perhaps it’s that variation that makes it so engaging.