On February 27th 1962, my husband and I were lucky enough to hear Maria Callas, accompanied by the Philharmonia, singing various operatic arias ( I have the prorgamme).  We could only afford one ticket so my husband heard the first half and I took the seat after the interval.  I was pregnant at the time and had been in hospital for several weeks but was allowed out especially for the concert During the Carmen, Suite No. 2, the baby became very excited and I'm sure the whole row oseats was shaking!  Our son was born soon after and has always loved Opera and our 2nd son, a freelance percussionist, plays regularly with the Philharmonia Orchestra in the Festival Hall.  The Callas concert, was, of course, a "sell-out " - I shall never forget it.