I Don't Know That Song

"I know that one but I can't do it". This quote from a book about improvisation got me thinking; What is the difference between knowing and being able to perform something? And how does that difference shift based on if the performer reads music or plays by ear?

I was trained to read music so for me, knowing a piece means I can play it reliably well when the music is in front of me. But take that music away and I am suddenly at sea even with simple tunes that can turn into ear-worms. I can often fake a harmony line or even stumble through the tune (after a few false tries) if it is a simple song but I won't really retain it based on that alone. The interesting thing is that I clearly "know" the tune because I recognize whenever I hit a wrong note, flub a rhythm or miss an entrance. For that matter, I also recognize when I get it right! 
I find that learning a piece by ear, even a short repetitive folk tune, can take a startlingly long time compared to reading the sheet music. Having to recognize when a note is right or wrong AND work out the technical details of playing it AND commit the song to memory all at the same time doubles or quadruples the time required to learn the piece. I often get wildly frustrated and say, "just find me some sheet music, it will be faster". But the tunes I have learned by ear I KNOW. They are in my head, my fingers and sometimes simply spring out of the flute without any conscious plan to play them. Even the music I have memorized after learning to play them from sheet music don't take up quite the same space in my mind.

So here are some of the conclusions I have come to; 
Those who habitually play by ear can recognize a tune without knowing it well enough to play by themselves. This doesn't mean they can't play along with a group since they often can come up with something reasonably close based on knowing similar tunes or simply having absorbed the style of music (much easier to do when you spend such intensive amounts of time on every single song). 
Those who usually read music can play a tune with the notation in front of them but may have trouble jumping in with a group that is playing from memory. On the other hand, they can play a wide range of tunes using the sheet music with relatively little prep time. They can even switch styles with reasonable accuracy based on having studied so many different styles (much easier to do if you aren't spending quite as much time learning every single song). 
Additionally, musicians in both groups may develop the ability to fake a tune or a harmony line based on what others are doing. Oddly, this skill is not generally taught in spite of how useful it is in almost all musical situations. Maybe because it feels like cheating to so many musicians, hence the term "fake". What we are actually doing is improvising, often at a very skilled level.

It seems to me that there is a wide range of "knowing" music, ranging from simply recognizing a familiar melody to having each turn and twist committed to soul deep memory. And somewhere in-between, each musician comes up with a sweet spot that let's them know, perform, teach or ornament a tune to the audience's (and their own) satisfaction.

Playing a piece I have halfway memorized and the odd faces I make in the process.