Singing and Whistling

Jimmy Durante liked to "start the day with a song". The trouble is that if I do (in my head rather than vocally, under the shower) it stays with me for the rest of the day.
I remember going to a symphony concert in Cardiff when I was a student and hearing Sibelius's 2nd Symphony; the next day I heard various versions of the famous tune of the last movement in the corridors of the college: those who attended the same concert were heard to be either humming or whistling it pretty well all day.
Once that tune gets into my head it stays there for hours if not a day if not days.
Again, the final movement of Sibelius's 5th Symphony - though it's difficult to hum, sing or whistle the final bashing notes; all you can do is think them.
Thinking tunes is an odd practice though it must have been what Beethoven did when he went deaf. At the first performance of his 9th. Symphony, which he conducted when he was completely deaf, he could not hear the applause at the end and a member of the orchestra turned him about to face the audience. He could "hear" his own music but he couldn't hear the applause.
I tend to whistle rather than sing chiefly, I suppose, because I feel that my singing would be too unpleasant to others.
Georg Bernard Shaw did not sing in the morning (to my knowledge) but it is a recorded fact that before he retired for the night he sang long and loud, not just one song that had stuck in his mind but heaps of them: arias from Mozart particularly. I wonder if his wife welcomed it or put in her ear plugs.
If his singing compared with his acting abilities it wasn't up to much. Sybil Thorndike used to tell of Shaw's occasional visits to rehearsals of his plays and how he used to show them how it should be done - "he was hopeless" she maintaned.
What I've got in my head at the moment is "Many a teardrop will fall/ But it's all/ In the game...." (Nat King Cole is singing it).