Coldplay\'s Chris Martin
Coldplay's singer Chris Martin Slaven Vlasic/Getty Images

Chris Martin has an interesting choice of words to compliment Rihanna's voice. According to the Coldplay frontman, the Diamonds singer voice is "like a beautifully squeezed tube of toothpaste".

In an interview with the Guardian, Martin said: "Rihanna has a thick one, so it's very hard to annoy anybody. It's like a beautifully squeezed tube of toothpaste." The Coldplay frontman also called Rihanna the "Frank Sinatra of our generation".

He said: "She can turn anything into gold with that voice. Here's the thing: if you speak to a good singing teacher about great opera singers, they will talk about consistency of tone. Or there's a book by Alfred Tomatis about why some people like certain people's voices and other people hate them, like Bob Dylan or me or whoever. 'Oh, I hate that voice.' So there's this thing about people's frequency responses -- what they are pleased by."

Martin and Rihanna collaborated on Coldplay's 2011 hit, Princess of China. "When you think of Rihanna's voice you think of this whole, rich thing, solid like a tree trunk. And Drake is pretty similar, but Rihanna's voice is just delicious for your ear," the 39-year-old British singer added.

The Clocks singer also spoke about Coldplay playing at the Super Bowl with Beyoncé and Bruno Mars in February. He said: "We thought – this is not going to read so well, but it's the truth, so I'm going to tell you – we thought: 'Let's embrace as much of our world, the musical world, as possible.' The kids on strings were all from Gustavo Dudamel's Sistema orchestra in inner-city LA, a programme invented in Venezuela. Bruno is from Hawaii, Beyoncé is from Texas, and she's the greatest dancer in the world, and the greatest artist, and Bruno's pretty close. So, really, the idea was to present something of togetherness."