AGO Organ Registration & Tonal Design 2 — Questions and Answers
Question 1: Which stop family produces tone by causing a metal reed to vibrate against a shallot?
- Flue pipes
- Reed pipes (Correct answer)
- Gedackt pipes
- String pipes
Correct answer: Reed pipes
Reed pipes use a vibrating brass tongue (reed) beating against a shallot to produce their characteristic sound.
Question 2: A 'Quint' stop sounds at which interval above the written pitch?
- An octave
- A fifth (Correct answer)
- A third
- A seventh
Correct answer: A fifth
A Quint (or Nazard at 2 2/3') sounds a fifth above the unison pitch, reinforcing the third partial of the harmonic series.
Question 3: When building a full registration from scratch, what is the standard foundational order?
- Reeds → Mixtures → Principals → Flutes
- Flutes → Strings → Principals → Reeds
- Principals → Flutes → Mutations → Mixtures → Reeds (Correct answer)
- Mixtures → Principals → Flutes → Reeds
Correct answer: Principals → Flutes → Mutations → Mixtures → Reeds
The classic approach adds principal chorus stops first, then flutes, then mutations and mixtures, with reeds last to crown the ensemble.
Question 4: The term 'Céleste' in a stop name (e.g., Voix Céleste) indicates what acoustic phenomenon?
- The stop is tuned a semitone flat
- Two ranks slightly mistuned to produce a wavering beat (Correct answer)
- A stop voiced with extra wind pressure
- A rank that sounds two octaves above unison
Correct answer: Two ranks slightly mistuned to produce a wavering beat
A Céleste consists of two ranks — one at normal pitch and one slightly sharp — whose interference beats create a gentle, undulating effect.
Question 5: Which characteristic best distinguishes a Gemshorn from a Gedeckt?
- Gemshorn is a reed stop; Gedeckt is a flue stop
- Gemshorn has a tapered (conical) body; Gedeckt has a stopped cylindrical body (Correct answer)
- Gemshorn speaks at 16'; Gedeckt speaks at 8'
- Gemshorn uses higher wind pressure than Gedeckt
Correct answer: Gemshorn has a tapered (conical) body; Gedeckt has a stopped cylindrical body
The Gemshorn is an open, conically tapered flue stop, while the Gedeckt is a stopped cylindrical pipe, giving each a distinct tonal quality.
Question 6: In French Baroque organ literature, the 'Grand Jeu' registration typically combines which stops?
- Fonds d'orgue (8' and 16' flues only)
- Bourdons, Montres, Prestant, Jeux de tierce, and Trompette/Clairon (Correct answer)
- Full organ with all mixtures and reed stops
- Cornet and Cromorne only
Correct answer: Bourdons, Montres, Prestant, Jeux de tierce, and Trompette/Clairon
The Grand Jeu is a bright, festive registration combining foundation stops with tierce mutations and reed chorus stops such as Trompette and Clairon.
Question 7: What is the primary acoustic function of a Mixture stop?
- To add 16' bass reinforcement
- To reinforce upper harmonics and brighten the ensemble (Correct answer)
- To provide a solo melodic color
- To create sub-octave resonance
Correct answer: To reinforce upper harmonics and brighten the ensemble
Mixture stops reinforce the upper partials of the harmonic series, adding brilliance and blend to the principal chorus.
AGO Organ Registration & Tonal Design 2
Which stop family produces tone by causing a metal reed to vibrate against a shallot?