Evensong = Chanted Evening Prayer
The monastic communities of ancient Christendom typically gathered for prayer 8-9 times a day. Their life was dedicated to ever-increasing communion with God through prayer. The call of the ordinary Christian is no different. The English reformers, knowing the rather large difference between the life of a monk and the life of us ordinary folk, condensed the 8-9 daily monastic prayer services down to 2, known as the Daily Offices, also affectionately known as Morning and Evening Prayer.
Christians around the world say Evening Prayer at the time of sunset, and Christians around the world chant Evening Prayer at sunset on the Eve of Major Feasts of the Church (Christmas Eve, All Hallows Eve, etc.).
Chanting is a tool the ancients used to give honor to a text. It elevates the words of Scripture above the common daily use of speech and thus elevates its honor. Therefore, Evensong = Chanted Evening Prayer!