Saw "Quare Fellow" done in Gr. Village (Circle in the Square??) in 1950s(late?).  The Clancys were in it(Tom & Liam &, I think, Paddy).  The song was obviously about life in the prison, & the sound of "next thing" signal: wake up, straighten up cell, go to breakfast, do next task, etc., go to bed.  I was under 19.Years later, back home in Texas with my youngest child in trouble & in jail, hubby & I go to see him there.  Every step into/out of that visit was accompanied by a terrible loud, metallic, mechanical clanking.  All "doors" opened & closed with that sound.  I reflected on the fact that the guards' movements through the halls & cell blocs would be accompanied by that hideous noise 24/7.  It must be a hated sound (I hated it by the second time it happened that visit).  A song made about such a sound would be an attempt to belittle or lessen the power of that awful noise.  I assure you that the triangle sound in the play was in NO WAY musical.