LONDON—According to sources close to the English folk-rock quartet Mumford and Sons, the band’s members were surprised to discover during their annual Christmas gift exchange Wednesday that they had all gotten each other new mandolins. “I love my mandolin so much that I decided this was the year to introduce Ted [Dwane], Ben [Lovett], and Winston [Marshall] to this wonderful instrument,” said lead singer and guitarist Marcus Mumford, whose bandmates confirmed they each independently decided to buy each other mandolins with the exact same thought in mind. “To be honest, I thought at least some of the 12 mandolin-shaped packages would turn out to be banjos, dobros, or buzuqs when we unwrapped them. But I can’t say I’m disappointed when I think about the amazing sound we could create with this many mandolins.” Mumford added that the coincidence was at least an improvement over last year’s exchange, when each of the four musicians went home with three copies of the band’s debut EP, Love Your Ground.