It should be a favourite song of your special person or one which they can relate to easily and certainly one which is familiar to everyone present. You may need to ask around if you are not sure: please provide a couple of song choices.
We suggest sticking to a straightforward song with a verse and chorus structure.
Well known traditional folk songs such as “Ilkley Moor Bar T’at” work well as the structure is straightforward and groups of people can sing it easily. Equally most pop songs lend themselves to this treatment as well: e.g. “Livin La Vida” is a fast paced song with a straightforward structure.
Your choice can be by any singer or group : The great singers of the past: Frank Sinatra, Bing Crosby, Barbara Streisand, Matt Munro, Bob Marley as well as Lionel Ritchie, Adele and Emeli Sandé , any artist as long as the song can be sung karaoke style! Musicals can provide suitable sources too.
A happy song is probably better than a sad one but I am sure even Leonard Cohen’s lyrics can be adapted for the purpose!