The booklet names the artists without indicating their vocal range. Whilst most are obvious (i.e. Peter Pears is a Tenor), the credited vocals have been obtained from: https://brittenpears.org/explore/benjamin-britten/music
The ensemble for Disc 12 Track 12 (The Sword In The Stone) is just specified as Instrumental Ensemble without specifying any musicians (unlike the Instrumental Ensemble for tracks 15 and 16 on the same disc).
The Beggar's Opera: Recorded at Snape Maltings, 7-11 June 1992 Noye's Fludde: Recorded at Orford Church, Suffolk, 3-4 July 1961 The Golden Vanity: Recorded at St John's Smith Square, London, 10-11 October 1969 Curlew River: Recorded at Orford Church, Suffolk, 8-12 June 1965 The Burning Fiery Furnace: Recorded at Orford Church, Suffolk, 23-27 May 1967 The Prodigal Son: Recorded at Orford Church, Suffolk, 21-22 May 1969 The Little Sweep (Let's Make An Opera): Recorded at Decca Studios, West Hampstead, London, 1-2 October 1955 & 22 January 1956 Children's Crusade: Recorded at St John's Smith Square, London, 10-11 October 1969 The Prince Of The Pagodas: Recorded at Walthamstow Assembly Hall, London, 13, 16, 17, 19 & 21 February 1957 Plymouth Town: Recorded at Studio 1, BBC Maida Vale, London, 22 June 2005 Film Scores: Music recorded at CBSO Centre, Birmingham, 11-12 March 2006, Narration recorded at The Sound Company, London, 10 July & 29 September 2006 Love from a Stranger: Recorded at Studio 1, BBC Maida Vale, London, 2 March 1999 Johnson over Jordan: Recorded at Abbey Road Studios, London June/July 1990 The Rescue of Penelope: Recorded at BBC Studio 7, Manchester, 22-23 April & 4-5 November 1995 The Company of Heaven: Recorded at Henry Wood Hall, London, June 1989 The Sword in the Stone: Recording and Production details unknown Russian Funeral/The Eagle has Two Heads: Recorded at St Jude-on-the-Hill, Hampstead, London, 27-29 July 1979 On the Frontier/This Way to the Tomb: Recorded at Rosslyn Hill Unitarian Chapel, London, 28-30 October 1992 Barcode: 028947854494 Other: 478 5504 (Catalogue# CD1) Other: 478 5505 (Catalogue# CD2) Other: 478 5506 (Catalogue# CD3) Other: 478 5507 (Catalogue# CD4) Other: 478 5508 (Catalogue# CD5) Other: 478 5509 (Catalogue# CD6) Other: 478 5510 (Catalogue# CD7) Other: 478 5511 (Catalogue# CD8) Other: 478 5512 (Catalogue# CD9) Other: 478 5513 (Catalogue# CD10) Other: 478 5514 (Catalogue# CD11) Other: 478 5515 (Catalogue# CD12) Label Code: LC 02869 Rights Society: BIEM Rights Society: SDRM Matrix / Runout: 00289 478 550-4 01 + 53255740 (CD1) Mastering SID Code: IFPF LV27 (CD1) Mould SID Code: IFPI 0128 (CD1) Matrix / Runout: 00289 478 550-5 01 + 53255742 (CD2) Mastering SID Code: IFPF LV27 (CD2) Mould SID Code: IFPI 0146 (CD2) Matrix / Runout: 00289 478 550-6 01 * 53255841 (CD3) Mastering SID Code: IFPI LV26 (CD3) Mould SID Code: IFPI 0128 (CD3) Matrix / Runout: 00289 478 550-7 01 * 53258553 (CD4) Mastering SID Code: IFPI LV26 (CD4) Mould SID Code: IFPI 0133 (CD4) Matrix / Runout: 00289 478 550-8 03 + 53258555 (CD5) Mastering SID Code: IFPI LV27 (CD5) Mould SID Code: IFPI 0123 (CD5) Matrix / Runout: 00289 478 550-9 01 * 53258557 (CD6) Mastering SID Code: IFPI LV26 (CD6) Mould SID Code: IFPI 0131 (CD6) Matrix / Runout: 00289 478 551-0 01 # 53254813 (CD7) Mastering SID Code: IFPI L787 (CD7) Mould SID Code: IFPI 0149 (CD7) Matrix / Runout: 00289 478 551-1 01 * 53258559 (CD8) Mastering SID Code: IFPI LV26 (CD8) Mould SID Code: IFPI 0123 (CD8) Matrix / Runout: 00289 478 551-2 01 # 53254815 (CD9) Mastering SID Code: IFPI L787 (CD9) Mould SID Code: IFPI 0125 (CD9) Matrix / Runout: 00289 478 551-3 01 + 53259547 (CD10) Mastering SID Code: IFPI LV27 (CD10) Mould SID Code: IFPI 0128 (CD10) Matrix / Runout: 00289 478 551-4 01 # 53254817 (CD11) Mastering SID Code: IFPI L787 (CD11) Mould SID Code: IFPI 0146 (CD11) Matrix / Runout: 00289 478 551-5 01 + 53254819 (CD12) Mastering SID Code: IFPI LV27 (CD12) Mould SID Code: IFPI 0133 (CD12)