Does anyone know to what the custos refers at the beginning of the chants in Chants Abreges? For the Gradual one could guess that it is related to the chanting of the Epistle. But the Alleluia has a custos that I can't always compute to be referring to the end of the Gradual that precedes it. See, for example, p. 79 Gradual and Alleluia for X. Dimanche apres Pentecote.
I see no explanation in the book.
To participate in the discussions on Catholic church music, sign in or register as a forum member, The forum is a project of the Church Music Association of America.