John Legend thinks Kanye West is "generous" and "passionate", despite many of his comments being "impolite".

The 35-year-old singer and Kanye, who turns 37 on Sunday, were introduced by producer and songwriter Devo Springsteen in 2001 and the pair have gone on to become close friends.

Kanye acted as producer on two of John's albums; his debut Get Lifted and his recent offering Love in the Future. In turn John performed at Kanye's recent wedding to reality TV star Kim Kardashian.

Many people view the Bound 2 musician as egotistic and brash, but John insists there is more to Kanye than the impression he gives off.

“Well, I mean, he says what he says. And obviously a lot of these things he says are impolite. Or, things that people aren’t use to hearing people who care about their image saying!” John laughed to British newspaper The Independent.

“But I’ve seen all sides of him: I know how generous he can be, how passionate he is about art and creativity, and how much he truly loves making music and designing clothes and making ideas.

“People see negativity coming from him sometimes, but what I see is his true love for art and music. And that makes him one of the most important and prolific and creative artists we have in the business.”

John has been married to model Chrissy Teigen since September last year and the couple often put on public displays of affection. His track All of Me features romantic lyrics such as "How many times do I have to tell you / Even when you're crying you're beautiful too," and John remembers the writing process behind it. He co-penned the tune with songwriter Toby Gad after Toby's manager emailed John.

“[Toby's manager] is an old friend of mine and she said I should write a song with a similar message as Billy Joel’s She’s Always a Woman. She knew my relationship with my then-future wife, so she thought I should write a song like that to Chrissy," John explained.