I think the ban on music applies to before and after Mass, as well as during the Mass itself.
From the 2002 General Introduction to the Roman Missal (GIRM) approved for the USA, which can be accessed from
romanrite.com/girm.html :
“313. … In Lent the playing of the organ and musical instruments is allowed only to support the singing. Exceptions are Laetare Sunday (Fourth Sunday of Lent), Solemnities, and Feasts.”
It could be argued that this is from the Roman Missal, which just gives the rules for Mass. So this instruction from the Ceremonial of Bishops is helpful. It is from Part IV “Celebrations of the Mysteries of the Lord Through the Cycle of the Liturgical Year”, Chapter 3 “Lent”:
“252 During Lent the altar is not to be decorated with flowers, and the use of musical instruments is allowed only to support the singing.”
(Ceremonial of Bishops, Liturgical Press, 1989, ISBN 0-8146-1818-9, page 89).
This is not just talking about Mass, but Lent more generally. In the paragraph before it has: “251. … The faithful should be urged to take a greater and more fruitful share in the Lenten liturgy and penitential services. They should be advised particularly to approach the sacrament of penance during Lent, …”.
Chapter 5 has the title “Liturgical Assemblies During Lent”. It describes the procession to the church with the bishop for a Mass, celebration of the word of God or penitential service.
Also applying to these are the instruction: “252 During Lent … the use of musical instruments is allowed only to support the singing.” So it also applies to before and after Mass.
It is talking about public church ceremonies. So I do not see it as a ban on playing the organ at home as part of learning or practice. But I do not see it as only applying to the start and finish of Mass.
