It happened on Thursday when the BBC SSO was joined by the BBC Singers for a brace of concerts in Glasgow and Ayr.
I know the legendary status of the BBC Singers. They are an elite, professional ensemble of singers and of course I've heard them before, live and on radio. But, hand on heart, none of this prepared me for the musical equivalent of a slap in the face at their astounding performance with the SSO, conductor Bernard Labardie, and a brilliant quartet of young soloists, of Haydn's Mass In Time Of War, a performance which had me transfixed by the beauty, power, clarity, intensity, and the sheer sense of purpose and focus with which the BBC Singers and the young soloists brought the Mass so vividly to life.
It was a performance of absolute unity, with a flawlessly balanced and immaculately articulate choral sound; a sound, moreover, that not once generated the impression of an ensemble at full tilt: there was, in every movement, whether the music was fast, slow, loud or soft, a sense of understatement, of an ensemble with masses in reserve. And what emerged from that was an account of the Mass which reflected the conciseness and succinctness of Haydn's great musical creation: it is a piece that is absolutely to the point.
Labardie's Mozart 39, however, was a bit less to the point: too fussy, almost prissily so, in its over-polished expressivity.