The music font "Volpiano" is named after William of the Volpiano (also known as William of Dijon, or Fécamp), the great 11th-century reforming abbot. The manuscript Montpellier, Bibl. de l'Université, H 159 may be connected with his work. As is well known, Montpellier H 159 notates chants of the mass with both neumes and alphabetic letters running from a to p.
See Michel Huglo, 'Guillaume de Dijon', in The New Grove Dictionary of Music and Musicians, Revised Edition (London 2001), vol. 10, p. 536; Alma Colk Browne, 'The a-p System of Letter Notation', Musica disciplina 35 (1981), 5-54. Alma Colk Santa-suosso, Letter notations in the Middle Ages, Musicological Studies vol. 52 (Ottawa 1989).