Players who have improved the most during their career?

[princeplanet]

Sonny Rollins' whole bridge experience is a pretty popular part of jazz history. Legend has it, after hearing Coltrane play, he took 3 years off to shed underneath a bridge for about a thousand hours every day. He came out the other side a completely different player and cut an amazing album afterwards called The Bridge.

I get hauled over the coals for this, but I prefer all Rollins (very) early work to his post Bridge output. "Chasin' the Trane" was a regrettable choice in his case, in my extremely humble and ignorant opinion...

[HrundiV.Bakshi]

Chris Whiteman.
His playing on his videos get better over time.

[bleakanddivine]

There are a lot of musicians who started out with only a rudimentary knowledge of playing an instrument but over time became reasonably accomplished.

Ian Anderson pretty much learned the flute on Jethro Tull gigs, having started out on guitar/harmonica.

[jameslovestal]

Steve Kahn is someone that has really grown as a musician over the decades. When I first heard him with Larry Coryell, my friends and I would joke that he sounded like us,,, which was not-so-good. This became more clear when we would listen to the Coryell \ Philip Catherine recordings. Kahn wasn't at their level. Of course Kahn had a musical heritage from his father, Sammy.

The recordings Kahn has made in the last decade or more are that of a first rate musician.

[Doctor Jeff]

Ian Anderson pretty much learned the flute on Jethro Tull gigs, having started out on guitar/harmonica.

True. He said in interviews he had to do something with his hands, and he already had a great guitar player, so he took up the flute.

I have to say technical or not, he's one of the most entertaining flute players out there.

[44lombard]

Steve Kahn is someone that has really grown as a musician over the decades. When I first heard him with Larry Coryell, my friends and I would joke that he sounded like us,,, which was not-so-good.

Kahn wrote on his blog/website:

When I moved to New York in January of 1970, I thought that I was arriving ready to play, ready to be an artist and to pursue my dream of becoming a great Jazz guitarist and musician. I arrived only knowing two people: David Friedman(vibes) and John Miller(ac./el. bass). It didn't take too long to realize that upon arrival, I was NOT the musician that I had thought that I was - or, better said, that I hoped that I was. David Friedman, who is one of the greatest musicians that I have ever had the privilege to know and work with quickly recognized my shortcomings, and, in a quiet moment, suggested that I go and take some lessons from the great Jim Hall. And so, as I knew that David was right, I phoned Jim, made an appointment, and began my studies....Eventually, I discontinued my studies with Jim, because I didn't feel that I was getting what I needed from him. It was not his fault, again, I just wasn't ready to be his student!
Jim Hall "Careful!" Solo Transcription and Analysis by Steve Khan

It's a great little essay about studying with Hall and Hall's playing, with a coda about John Abercrombie. I can imagine growing up in Hollywood in the 50s and 60s with your successful show-biz dad being a buddy of Frank Sinatra's could make life seem a little easier than it is as a young man.