Brothers: A Tale of Two Sons OST - Naia by Goldielou

Composer: Gustaf Grefberg (Enclave, Knights of the Temple, The Chronicles of Riddick: Escape from Butcher Bay & Assault on Dark Athena, The Darkness, Payday 2, A Way Out…) / Performers: Emma Sunbring (vocals), Christopher Öhman (viola), Simon Viklund (additional instruments)

This high-pitched vocal technique is called "kulning": it comes from an ancient Scandinavian herding call.
⚠️SPOILER⚠️ After controlling both brothers together throughout the adventure, the player finds himself alone with the younger (Naiee), as Naia (the elder) was fatally injured before he died. This is where this music can be heard in the game.

This is a shortened version (original track length: 2'32).