the pipe organ!
According to a Second
Vatican Council document: “In the Latin Church the pipe organ is to be
held in high esteem, for it is the traditional musical instrument which
adds a wonderful splendor to the Church's ceremonies and powerfully
lifts up man's mind to God and to higher things.
instruments also may be admitted for use in divine worship, with the
knowledge and consent of the competent territorial authority, as laid
down in Art. 22, 52, 37, and 40. This may be done, however, only on
condition that the instruments are suitable, or can be made suitable,
for sacred use, accord with the dignity of the temple, and truly
contribute to the edification of the faithful.” (source: Constitution
on the Sacred Liturgy – Sacrosanctum Concilium, solemny promulgated by
His Holiness Pope Paul VI, Dec. 4, 1963)
(General Instructions for the Roman Missal): "While the organ is to
be accorded pride of place, other wind, stringed, or percussion
instruments may be used in liturgical services in the dioceses of the
United States of America, according to longstanding local usage,
provided they are truly apt for sacred use or can be rendered apt."