The Choral Bass is a pedal stop, although somewhat unusually for a pedal it is voiced very high, usually in 2' or 1' pitch. It is designed to play in chorales
The Clairon is essentialy an octave Trompete. There is not really much to say about it.
The Clarinet is a reed stop with long, fluelike resonators. It is considered the one of the most accurate imitative stops. It has a sound that is very similar to the clarinet, which is probably due to the fact that reed stops function in the same way as a clarinet.