He said that, if you are in a club and can see the musicians, it is easy to pick out the sound of each instrument. But when you are at home listening to recordings, it can sometimes be difficult to do so.
Maybe his theory is correct. I like listening to string quartets and I can tell you I find it very difficult to distinguish the viola from the cello when I'm listening to the radio or a CD.
This led me to think about wider issues concerned with listening.
Despite not being all that brilliant as a player, I am lucky enough to be asked to play in various bands from time to time. And I am often surprised at how limited the listening skills of the audience seem to be. If we make a horrible mistake (it certainly happens), nobody in the audience even blinks an eyelid. Play something really badly and people tell you how great your music is. Play something really well and nobody takes any notice.
I also have accumulated plenty of evidence that many people can't tell which instruments which sounds are coming from - except when it is blindingly obvious - when someone takes a solo at the front of the stage.
Bass players, banjo players and guitarists fare particularly badly. I'm sorry to say the typical audience member hardly notices their individual skills, except on the rare occasion when they are given a solo chorus. Ask someone what he thought of the string bass player's contribution to the ensemble and he tells you he didn't notice.
It's the same with visual skills. I remember once playing in a quartet for a couple of hours in a church with a seated audience. At the end, a gentleman came up to us to ask whether we could play at a birthday party the following month. As we reached for our diaries, he said - to our amazement - 'Now how many of you are there? Five, isn't it?'
Similar was the occasion when I played in a quartet of guitar, tuba, clarinet and trumpet. At the end of our first set, we were told: 'We're going to draw the raffle now. So can we have a roll on the drums please?'
How unobservant audiences can be!
I have also met people who have attended good jazz performances and yet can't recall anything about them - apart from a joke made by the leader or the fact that someone put some funny words to a well-known song. Ask them how good the string bass player was and they don't even remember whether there was a bass player.