I've left this thread alone until now just browsing it as it's recurred but Barbara's post makes me want to add my bit.

I'm firmly of the opinion that the ISB's words did sink deeply into the memories of the folk who saw them at the time and in their place. This seems to be confirmed by the various postings by "persons of a certain age" above :)

Still with me now certainly; An October doesn't go by without singing October Song; I never see a hedghog but the words of The Hedgehog's Song pop into my mind.
And at other times:
Everything's Fine Right Now, First Girl I Loved, Invocation, Log Cabin Home in the Sky, Maybe Someday, Painting Box, Way Back in the 1960's, When the Music Starts to Play, You Get Brighter.
These might be my favourite ISB songs. They're the ones I can remember at the moment anyway.

I believe that the songs stay with us because they have such gentle lyrics combined with a good level of humour.

AndyG