Testaments are a London-based romantic jazz quintet led by bassist and songwriter Mark McQuillan. Their music combines detailed songwriting with improvisational freedom built into the arrangements, leading songs to change substantially from one performance to the next.

The music moves between sparse, intimate sections and much louder, more chaotic peaks, while the song and lyrics remain the anchor throughout. Rebecka Edlund’s theatrical vocal style is central to the sound, and euphonium often takes a distinctive soloistic role. Testaments aim to take listeners through a wide range of emotions, from ecstatic joy to tenderness and mourning. The songs deal in heightened situations, and the band pushes the material in different emotional directions each time they play.