Can you guess which Christmas song is being sung in Gregorian chant?

Omnia quae pro natale christi cupio, sunt tu! Tori Longdon sings Mariah Carey and Walter Afanasieff’s 1994 hit ‘All I Want for Christmas is You’ in 9th-Century plainsong. The music shown on screen are neumes, early musical notation that predates the five-line staff notation. Although chant was probably sung since the earliest days of the Church, for centuries it was passed down only orally. Around the 9th century, neumes emerged as visual aids to guide the proper melodic recitation of chant. These earliest neumes were simple inflective marks, indicating the general shape of the melody rather than precise pitches or rhythms.