The answer is they produce a sublime sound which is melodious, gentle on the ear and the choice for Friday's French music break this week.
Elisa Tovati and Tom Dice (screenshot from official video)
The actress is 35-year-old Elisa Tovati from France who has built up a solid if not remarkable career in television and cinema.
Elisa Tovati (screenshot from official video)
Along the way she has produced three albums.
Her latest is "Le Syndrome de Peter Pan" which is described on her official website as a "musical tale of a little girl who is all grown up."
And it's from that album that she has released the single "Il nous faut", a duet with the young Belgian singer Tom Dice.
Tom Dice (screenshot from France 5 performance)
Under his given name of Tom Eeckhout, he finished runner-up in the Flemish Belgian version of the TV talent show the X Factor in 2008.
But as Tom Dice, his name might be familiar to some Eurovision song contest fans as the 22-year-old sang his country's entry in 2010 in Oslo.
The song "Me and my guitar" finished a creditable sixth and didn't go unnoticed here in France picking up plenty of airplay.
Anyway back to the pairing of Tovati and Dice on "Il nous faut - and it's simply inspired.
Elisa Tovati and Tom Dice (screenshot from France 5 performance)
Neither of them has what you might call an outstanding voice; good certainly, pleasant to listen to and melodious. But not the sort that will make your jaw drop in admiration.
That doesn't matter though. The combination is a delight to listen to as their voices blend and they sing alternately in French and English.
From the opening bars of the guitar strings being plucked and strummed through to the violin and folksy feel of the melody, Tovati and Dice treat you to an almost perfect pairing.
If you liked, for example, the 2009 hit "Lucky" by Jason Mraz and Colbie Caillat, the chances are you'll feel the same about Tovati and Dice singing "Il nous faut". There are definite similarities in the effect both the song and the voices have.
"Il nous faut" is perhaps very easy-listening, but that doesn't make it any the less enjoyable.
Just as a treat, here are two versions; the first is the official video and the second is a live performance they gave on France 5 television - proof that they can after all sing and reproduce the studio sound in front of an audience.
Elisa Tovati & Tom Dice - Il Nous Faut (Clip... par wonderful-life1989