LOL @stringy - ha, I like your recounting of your younger days there - at closing now on 70 years myself - I often think back.  Back in the mid 50's my own mum used to listen to the radio ("Home service" back in the day - I can still recall the names, the tone, and accent of the voices of the presenters!)  Once TV came around (and additional radio stations), she loved listening to stuff like Perry Como ( "Catch a Falling Star, and put it in your pocket, Save it for a rainy Day..... "  and so on) - I can hum/sing/play that (and many others I am afraid to say) on any instrument you care to name - OK - I may need a few days to get used to (trying to) play a clarinet - but - yeah.... I'd get close to the melody...  and there are hundreds of other tunes now stuck in my head over the years (mostly rock from the mid 60's to early 80's - after that - I stopped listening to Radio 1 and 2 ! LOLOL It became too much !!!!! )

But - if someone in a bar etc "called it out" and asked for some specific song or tune, well, if I even only half-way knew it - man - I'd give it a go - voice or instrument - it's just such a blast to "play with" well known tunes - even IF it is a "first-time-ever impromptu performance" and not-quite-right-or-complete - folks will recognise it and appreciate what's been done.  Can't get better than that!   Love it!