Elzee:
During Lent our cantor sings the prayers and the congregation sings the response ( ‘Lord Have Mercy’’, Christ Have Mercy, Lord Have Mercy). Can the cantor do this? I thought priest or deacon had to ‘lead’ the penitential rite prayers?
Yes, the cantor can lead this.
The 1984 Ceremonial of Bishops has it clearly: “When the third form of the penitential rite is used, the invocations are said by the bishop, by a deacon, or by another suitable minister.” (From Ceremonial of Bishops, Liturgical Press, 1989, ISBN 0-8146-1818-9, page 53.)
Also from the 2002 General Instruction of the Roman Missal:
“The Kyrie Eleison
52. After the Act of Penitence, the Kyrie is always begun, unless it has already been included as part of the Act of Penitence. Since it is a chant by which the faithful acclaim the Lord and implore his mercy, it is ordinarily done by all, that is, by the people and with the choir or cantor having a part in it. As a rule, each acclamation is sung or said twice, though it may be repeated several times, by reason of the character of the various languages, as well as of the artistry of the music or of other circumstances. When the Kyrie is sung as a part of the Act of Penitence, a trope may precede each acclamation.”
It is also in the Roman Missal’s Order of Mass. From the 1985 translation of the Roman Missal:
“The priest (or other suitable minister) makes the following or other invocations:
Priest: You were sent to heal the contrite: Lord, have mercy. …”. (From The Roman Missal, Catholic Book Publishing Co., New York, 1985, page 361).
From the 2002 Missale Romanum’s Order of Mass: “Postea sacerdos, vel diaconus vel alius minister, sequentes, vel alias, invocations cum Kyrie, eleison profert:” It allows a priest, deacon or other minister to lead the kyrie.
(From Missale Romanum, Libreria Editrice Vaticana, 2002, ISBN: 8820972719, page 508.)