Like the deacon, who would wear the dalmatic, the subdeacon could wear the tunic. However, out of a desire for less solemnity, both the deacon and subdeacon could omit the wearing of their traditional outer vestment. This would leave the deacon wearing a transverse stole over the alb and the subdeacon wearing only the alb. With the resulting Ministry of Acolyte in 1972, the vestment proper to this Ministry is now the alb (which is the vestment also common to Instituted Lectors). Any mention of the Tunic has now disappeared from the documents in relation to the OF since 1972, just as any mention of the maniple has not been seen since 1967. This would seem to spell the end of the Tunic for an Instituted Acolyte in the OF, but liturgical law is very interesting.
It is interesting to look at the mind of the Church in regards to the Ministry of Acolyte, does it not have any of the character of the subdeacon? In the apostolic letter Ministeria quædam, we find the following provision. Two ministries, adapted to present-day needs, are to be preserved in the whole Latin Church, namely, those of lector and acolyte. The functions heretofore assigned to the subdeacon are entrusted to the lector and the acolyte; consequently, the major order of subdiaconate no longer exists in the Latin Church. There is, however, no reason why the acolyte cannot be called a subdeacon in some places, at the discretion of the conference of bishops. There seems to be some connection in the mind of the Church.
Building on this we find in the Ceremonial of Bishops, n. 65:
"The vestment common to ministers of every rank is the alb, tied at the waist with the cincture, unless it is made to fit without a cincture. An amice should be be put on first if the alb does not completely cover the minister's street clothing at the neck. A surplice may not be substituted for the alb when the chasuble or dalmatic is to be worn or when a stole is used instead of the chasuble or dalmatic. When a surplice is worn, it must be worn with the cassock.
The last provision is very interesting. It is for the Bishop to approve other vesture. Other vesture has often come to mean, street clothes, but this need not be limited to it. Could not the Bishop approve the use of a Tunic for an Instituted Acolyte?
as these Dominicans once did.