AD LIBITUM. – This is an expression that has various uses in the liturgy. With regard to the “Rubrics,” it refers to the free use of certain “Collects” (v.). Musically, it concerns individual or collective recitative chants: individual, such as certain tones for Prayers, Epistles, Gospels, and Lessons; collective, such as various common tones of the Ordinarium Missae, including Kyrie, Gloria, Sanctus, Agnus, and also Credo. In ancient times, even the choice of the alleluia “Sicut volueris” was synonymous with a. l. In Ambrosian chant, on certain days there are some longer “melismas” or “iubilus,” to be used a. l. in the case of greater solemnity. In the interpretation of certain neumes, such as “stroficus,” a. l. may also be employed for the greater convenience of the choir. Guido d’Arezzo considered certain neumes a. l., although he maintained that in practice it was better to perform them.
Gregorio M. Suñol