It’s an article of faith among jazz musicians and educators that listening to jazz is crucial to learning to play jazz. This seems obviously true to me about jazz and about any style of music.
(Doubtless one of the reasons the jazz-initiated like to bang this drum, so to speak, is because most of Western music education is so notation-focused. The “classical” tradition has developed hand-in-hand with a notation system that does a pretty good—not perfect—job of breaking down classical music sounds into visual symbols. That system, unsurprisingly, works less well for non-classical styles like jazz. But jazz music is still often expressed in classical-type notation, with some kind of caveat, explicit or otherwise, that the player must apply some significant additional stylistic know-how that will override the usual meanings of some of the notation.)
But one thing classical music educators have done in their few hundred extra years is codify and explain many (not all, and not all well, and not all in agreement) of their stylistic and interpretive ideas. In jazz education, too often important details get waved away with a “ya gotta listen.”
“Ya gotta listen” to classical music to play it well, too. But there’s also more clear, thoughtful pedagogy available to help you know what to listen for, and how to apply it.
If you are a jazz educator and find yourself dodging questions or glossing over concepts with a “ya gotta listen,” can you add something to the picture? Try saying instead, “Ya gotta listen to how Cannonball Adderley ‘lays back’ in this particular phrase. He plays some notes later than expected in a way that sounds good. Listen a few times to see which notes, and how late.” Or: “Ya gotta listen to how Freddie Hubbard plays ‘outside’ over this turnaround. Can you figure out which scale he is drawing from? Where exactly does he resolve back to playing ‘inside?'”
How long would it realistically take for an unguided young musician to listen to jazz until they had fully absorbed the nuances? I used to feel pretty overwhelmed and hopeless when teachers three times my age with thousands of well-worn records told me I wouldn’t sound better until I had really listened. Luckily I had others who were willing and able to accelerate and focus my learning by giving some direction and context to my listening.
If you find that you have difficulty explaining some of the things you want your students to listen for, there are resources available to help you and them boil things down to understandable concepts. For improvisational theory, you might try free YouTube videos (or additional paid content) from teacher/players like Chad Lefkowitz-Brown or Aimee Nolte. For style, consider books like those by Caleb Chapman and Jeff Coffin or Ray Smith.
And yes, ya gotta listen.
If one was to include the composition of classical music in the realm of performing it then jazz and classical are just as complex to learn.