SOMERVILLE — At first blush the city’s bustling early music scene might not appear to have many artistic niches unclaimed. Yet a new group, Helios Early Opera, has recently staked out one of them, focusing on lesser-known repertoire served up in avowedly modern stagings, which themselves take place in unusual venues. When Helios recently staged Telemann’s “Pimpinone” at the Goodlife Bar, the group’s website made a seldom-heard case for the sybaritic side of period authenticity: “18th-century opera-goers enjoyed food and drink during performances, so why shouldn’t you?”

On Friday night at Somerville’s Center for Arts at the Armory, Helios offered Cavalli’s “Artemisia,” its third production to date, this one billed as a North American premiere.