Pop star Shawn Mendes surprised himself when he discovered how to hit the high notes using his falsetto voice last year (17).

The Stitches hitmaker, 19, was trying out vocal arrangements for his soulful new single when he tried - and succeeded - in holding the high pitch.

"Technically... last year, I couldn't sing falsetto," he tells Entertainment Weekly. "I figured out how to the day I wrote Where Were You In the Morning.

"You never discover you sing falsetto again; you just do, once. You never discover you can say a certain thing again; you just do."

The discovery is just one example of the many life and career transitions Shawn has made since his 2016 album, Illuminate, and he explains his growth is clear on his new self-titled third project.

"These songs are stamps of moments when I discovered what I was capable of," he says.

"(I've transitioned into) a lot of things. Between being a kid to being an adult. Transitioning from somebody who wasn't very confident in themselves musically to somebody who considers themselves a musician. And a lot of different things creatively, becoming so much more confident in what I do. I don't know, I just feel... different. I feel like I'm going through a change in a good way."

Shawn is also more open than ever about his emotions in his latest material, like opening up about his anxiety issues on the track In My Blood.

"The biggest thing I learned making this album is that if I am not writing 100 per cent the truth, I'm cheating myself, and the music just isn't going to be as good," he shares. "There were so many moments where I thought of a lyric and went, 'Oh, f**k, that's a little bit too honest.' But then I was like, 'Well, that's what makes it great - write it down! F**k it! Just take a hit!' Because that's what music is about. It's being honest."

Shawn's new album is released on Friday (25May18).