I'm currently suffering from an earworm. An earworm is a snatch of music that you can't get out of your head. In my case it's "The clouds will soon roll by", sung in 1932 by Elsie Carlisle, with Ambrose and his orchestra.
Somewhere the sun is shining
So, honey, don't you cry
We'll find a silver lining
The clouds will soon roll by…
This keeps popping into my head at odd moments throughout the day. I'm familiar with it from the sound track to the BBC series Pennies from Heaven but I haven't listened to it for ages. Why I should suddenly think of it now I don't know. Maybe the optimism of it appeals to me.