Evensong and Oratorio

Evensong noun - The sixth of the seven canonical hours of the divine office; early evening; now often made a public service on Sundays.

Oratorio and evensong are semantically related in religious song topic. In some cases you can use "Oratorio" instead a noun "Evensong".

Oratorio noun - A musical composition for voices and orchestra based on a religious text.

Evensong and oratorio are semantically related in chant topic. You can use "Evensong" instead a noun "Oratorio", if it concerns topics such as paean, religious song.