Kate Hudson, Avril Lavigne Sing Duet at David Foster's Star-Packed Wedding

Credit: Steve Granitz/WireImage ; Jason Merritt/Getty Images

Why'd they have to go and make things so complicated?

Canadian songwriter/producer David Foster said "I do" to model Yolanda Hadid on Friday, Us Weekly confirms. But the bride and groom weren't the only stars of the day: a source tells Us that Avril Lavigne and Kate Hudson sang a duet. (Hudson, 32, sang in Rob Marshall's 2009 musical Nine.)

Lavigne, 27, attended the ceremony with boyfriend Brody Jenner; Foster, 62, was married to Jenner's mom Linda Thompson from 1991 to 2005.

Fellow Canadian Michael Buble crooned at the reception, and Kenny G went from table to table playing his saxophone at dinner.

The groom's daughter, Erin, was in attendance with pal Samantha Ronson. Lindsay Lohan's ex "tried to DJ, but was told no," said a source.

This was the fourth marriage for Foster, who is known for composing tracks like "Grown Up Christmas List" and "I Have Nothing," as well as discovering artists including Buble, Josh Groban and Charice.