Similarish experience a couple days ago:
Was revising in the school library as I'm on study leave and was just going about my work quietly listening to music. Then a good song comes on and unawarely I start humming the tune and then start singing it but I did not realise I was doing it. So in the middle of the library filled with elder students everyone looks at me with a 'WTF' face whilst I'm singing and it was incredibly embarrassing.
I went bright red and just put my head down.
I feel for you Dezzy.
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ME AND GOD WE DON'T GET ALONG, SO NOW I SING