120 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. But other 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: Sacrosanctum Concilium (Vatican.va)