Tonus Peregrinus is a vocal ensemble specialising in early music and contemporary sacred music, especially that of founder and director, Antony Pitts. TP, as they are also known, has recorded a number of CDs for Naxos, their first winning the Cannes Classical Award (Arvo Pärt's Passio), and two albums of Antony Pitts' music for Hyperion Records – Seven Letters and Alpha and Omega. Their latest Naxos album, Music from the Eton Choirbook (8.572840) was recorded using a new microphone technique developed by NRK engineer Geoff Miles.

The ensemble sang at the memorial for Alexander Litvinenko.