One of the classic adages about songwriting is that the finished result will reflect the artist's mood at any given time. But that's not the case for Tom Petty, who says that he needs to have his head in a good place in order for him to write.

"Something horrible might happen, but you don't really write a song when you're feeling horrible," he told the CBC. "I mean, if I feel horrible, the last thing I'm going to do is look for a guitar to write a song."

That doesn't mean that Petty can't find a way to create during rough times. After all, this is a man who wrote one of his most-beloved songs, 'I Won't Back Down,' after somebody burned his house down. Instead, he waits until the difficult times have passed, at which point he can get the proper perspective.

"Maybe later, it's cathartic when you're happy again," he continued. "Maybe you can remember that and draw on it. But does it solve any probems? I don't think so. But I think you can moan on about your problems with songs. But I'm not one to write when I'm bummed out. I sort of go into a coma. I don't really go for the music then."

It's a long interview -- roughly 79 minutes -- but well worth the time for Petty fans. In it he speaks a lot about his creative process and the recording of 'Hypnotic Eye,' which will be released July 29. So far, he has issued five of the album's 11 songs for streaming. Petty and the Heartbreakers begin a two-month tour of North America on Aug. 3.