Tremulants appear in many varieties. Two main factors should be understood:
1. FREQUENCY is the speed with which the “cycles” or “beats” occur. The frequency of the tremulant in the first example (on the previous page, click the button to the right) is approximately six cycles per second--a relatively fast tremulant. Frequency, when used in this context, does not refer to pitch.
2. DEPTH is the amount of pitch or volume change that occurs from the points of highest to lowest wind pressure in the tremulant cycle. The depth can be classified as heavy, moderate, or light. The tremulant in the first example is moderate.
In most organs, pipe or electronic, these two factors can be adjusted by an organ technician.
TRY IT: Pull a 4' speaking stop on the Swell and the Tremulant. What is the frequency of the Tremulant? (Count the beats per second.) Does it seem heavy, moderate, or light?