A very good English clarinet player once told me: 'I know nothing at all about music. I play by ear. That's all you need for jazz.'
But on another occasion I overheard him saying to a pianist, 'You played a D minor chord in the third bar. It should have been F diminished.'
So much for 'knowing nothing about music'!
That gentleman died five years ago, but I have met several other musicians who have also proudly claimed they can't read music and know nothing about it. Presumably they thought they were natural geniuses.
I have become sceptical about such claims.
I can recall only three gentlemen who obviously could not read music and played entirely 'by ear'. But they were very limited in what they could offer in traditional jazz bands and in their understanding of tune structures and conventions. I noticed they were unable to gain acceptance in any regular band and managed only to pick up occasional gigs as deputies.
Of course, the ear is an essential tool in the learning of tunes when - as often happens - you can't get hold of printed music. Play along a few times with a good clear recording. Use the pause button and write the tune down as you go along. You may even be able to work out the chord progression reasonably well. I am sure most jazz musicians have mastered dozens of tunes in this way. But you need to know what you are doing. You must have at least some rudimentary understanding of keys, note lengths, time signatures and tune structures.
Many of the older generation of traditional jazz players depended very much on their ears in order to learn music, as they put it, 'closely enough for jazz'. But the younger generation is more academic in its approach to the repertoire. Some have studied both jazz and classical music at colleges. So they practise hard to memorise correctly the melodies, harmonies, structures, rhythmic patterns and grammar of the music. For an example of the finished product:
COMMENT RECEIVED FROM BARRIE MARSHALL:
I used to dep with a band that had a trumpet player who boasted he was an ear player and knew nothing at all about music. We were doing this gig in the back garden of a pub, we started a tune and on the first chorus the banjo player played a chord that was not right He played it again on the second chorus. Then when he played it on the third chorus the trumpet played turned to him and said, 'That should be a C7, not an F7!'