With so much fabric hanging from our shoulders, enough to make at least six purificators, people must be curious about what we do with the cumbersome appendages. Most of the time, we just let them dangle as they are, as we usually wear the Mozarabic surplice during penitential seasons. That dangling allows the sleeves to drag, and the dragging evokes penance and sorrow. Sometimes, we wrap the sleeves around our arms, and sometimes, we fold them.
As addendum to the first part, below is what we do with the surplus of fabric flapping about like a carefree kite from our shoulders:
During penitential times, that is, in Masses and in Offices in Adventide and Lententide, as well as in Masses and in Offices of the Dead, Cantors are not allowed to wrap their arms with the wings or sleeves of their surplices. In this case, they must let the wings or sleeves to dangle to the floor, that a sign of sorrow or grief might be given. Outside penitential times, Cantors are allowed to wrap their arms with the wings or sleeves of their surplices. During penitential seasons as well, in the presence of the higher or senior dignity of the Choir, junior Cantors are allowed to fold their wings or sleeves as a sign of humility. Outside penitential times, when Cantors wrap their arms with the wings of their surplices, they may opt not to fold them.
Tempore poenitentiae, id est in Missis Officiisque temporibus Adventus et Quadragesimae, sed et in Missis et Officiis Defunctorum, non licet cantoribus brachia sua alis vel manicis longis suorum superpelliceorum involvere. Hoc in casu, sinere alas vel manicas longas pendere ad solum debent, ut signum luctus vel moestitiae daretur. Extra tempus poenitentiae, licet cantoribus involvere sua brachia alis vel manicis longis superpelliceorum suorum. Tempore poenitentiae quoque, principiore dignitate Cappellae praesente vel seniore, iunioribus plicare alas vel manicas longas licet in signum humilitatis. Extra tempus poenitentiae, cum involvent cantores brachia sua superpelliceorum suorum alis, possint non plicare easdem.
Ut in omnibus laudetur Dominus.