The only known ranking of the angel species is the Producer.
Angels live in a separate and higher plane from the RG and UG. They created a social schema web to guide their activities. The Angels have their own "frequency" and the Composer can only pick up one frequency from the Angels, which would be the Producer's. (Secret Report 3, 4, 5)
There are also Fallen Angels who are considered criminals for breaking the Angel's code. (Secret Report 9, 11)