Simplify the following text for a Grade 6 native English-speaking person.
Original: Perhaps his most well known verse anthem is This is the record of John , which sets an Advent text for solo countertenor or tenor , alternating with full chorus .
Simplified: His famous verse anthem This is the record of John is often sung by choirs at Advent . It has a lovely solo for a countertenor who takes it in turns with the full chorus .