The couple that sings together, stays together – at least that's the case for Seal and Heidi Klum.

They are planning a duet on Seal's upcoming album, his rep confirms to PEOPLE, saying: "Heidi does sing on one song on Seal's new album System."

The track is called "Wedding Day," which Seal wrote for his model wife the day they got married in Mexico in May 2005.

"Family, my wife and children, that's my reason for being," Seal said last month. "I am finally in a content and happy place to the point where I feel like I need to sing about it."

In posting on his Web site earlier this year, the British singer wrote, "I am having a really good time making this record – there is an excitement in the studio a bit like the first record I made only this time with a lot more peacefulness."

Klum, 34, and Seal, 44, are parents to three children.

System, Seal's fifth studio album, is due out Nov. 13.

Klum's participation on the album was first reported by Perezhilton.com.