The musical tradition of the universal Church is a treasure of inestimable value, greater even than that of any other art. The main reason for this    pre-eminence is that, as sacred song united to the words, it forms a necessary or integral part of the solemn liturgy.
Sacrosanctum Concilium 112 from the Second Vatican Council

Below is a demo video of the Kyrie Eleison we are currently singing for Weekend Masses:

Artwork:Saint Cecilia and an Angel by Orazio Gentileschi (1563-1639) and Giovanni Lanfranco (1582-1647).