While St. Cecilia is frequently portrayed playing an organ, it is likely that she never played any musical instrument.
St. Cecilia is widely known as the patron saint of music, but did she ever play an instrument, or did she have a beautiful voice?
According to the Catholic Encyclopedia, she was not musical in any way, except for her “interior” music.
Medieval pictures of the saint are very frequent; since the fourteenth and fifteenth centuries she is given the organ as an attribute, or is represented as playing on the organ, evidently to express what was often attributed to her in panegyrics and poems based on the Acts, viz., that while the musicians played at her nuptials she sang in her heart to God only (“cantantibus organis illa in corde suo soi domino decantabat”); possibly the cantantibus organis was erroneously interpreted of Cecilia herself as the organist. In this way the saint was brought into closer relation with music.
The Golden Legend describes her wedding in a similar way.
When this blessed virgin should be espoused to a young man named Valerian, and the day of the wedding was come, she was clad in royal clothes of gold, but under she wore the hair. Hearing the organs making melody, she sang in her heart, only to God, saying: “O Lord, I beseech thee that mine heart and body may be undefouled so that I be not confounded.”
At the same time, some biographies claim that she would sometimes sing with both heart and voice.
Regardless of whether or not she played any musical instrument, or possessed a beautiful voice, it was her interior holiness that has inspired many musicians over the centuries. She remains the patron saint of music and she currently resides in Heaven, joining with all the other saints in singing to God a song of praise.