There are a few elements that reliably form the basis for an Alicia Keys song: heartache or infatuation, an essential tenderness and emotion made heavy with wisdom, a patiently unfurling melody and, of course, that voice, yearning and ready to break, even as it remains in control. Even though these building blocks have helped her stand apart from pop trends while forging a remarkable career, Keys says the making of a classic song is still a mystery to her.

Fifteen years after the release of her first album; 15 years after her first single, "Fallin'" went to No. 1 on the pop charts and became repertoire for televised singing competitions; 15 years after that first armful of Grammys, Alicia Keys says her songwriting has not become any more scientific. "Every time I write a song, I never know how it happens. And I kinda always wanna be like that," she tells Jason King in the latest episode of NPR Music's documentary series Noteworthy. "Some people are very mathematical writers, which is very intriguing. ... It's so opposite from me."

But, Keys says, "there are ingredients that make it more digestible. And for me, [that's] mostly a piano and a voice." Keys was drawn to the piano from an early age, and reaped benefits from the hours of practice she put in while friends were outside playing. "It provided me... focus, the ability to pay attention for a long enough period of time to make progress," she says. "And the actual knowledge of music, which then unlocked the ability to be able to write my own music and put my own chords and things I heard in my own head to different lyrics I felt. And I never, ever had to wait for anybody to write something for me."

In the earliest phases of her career, she says, artistic control was the first thing on her mind: "I would go into sessions already prepared with, 'Here's different groups of chords: I wrote this, I wrote this, I wrote this, I wrote this, I wrote this,' because they didn't believe that I could do all these things, that I could play and that I could produce and that I could actually write. I was like 15 years old, and they were like, 'I'm sure you have a cute little idea but let's get to the real music.'"

Since then, she says, she's learned that "if you try to control things too much, you miss the magic." Part of that has been a slow embrace of collaboration, though it was hard to let anyone into her writing process. "It's so vulnerable," she tells King. "Who wants to just bare their entire fears, insecurities, mistakes in front of people who can look at you and judge you and whatever? That's super, super scary."