A Dictionary of Music and Musicians/Bebung
BEBUNG (Ger.; Fr. Balancement; Ital. Tremolo), a certain pulsation or trembling effect given to a sustained note in either vocal or instrumental music, for the sake of expression. On stringed instruments it is effected by giving an oscillating movement to the finger while pressing the string; on wind instruments and in singing by the management of the breath.
The word Bebung refers, however, more particularly to an effect peculiar to the old clavichord, but not possible on the modern pianoforte, in which the continuous and uninterrupted repetition of a note was produced not by a fresh blow, but by a movement of the tip of the finger without leaving the key. This effect was formerly held in high estimation as a means of expression, and Emanuel Bach in the introduction to his 'Versuch über die wahre Art das Clavier zu spielen,' says, comparing the then newly-invented pianoforte with the clavichord, 'I believe, nevertheless, that a good clavichord possesses—with the exception that its tone is weaker—all the beauties of the former (the pianoforte), and in addition the Bebung and the power of sustaining the tone, inasmuch as after striking each note I can give a fresh pressure.'
The Bebung was not often marked, except sometimes by the word tremolo. Marpurg, however ('Principes du Clavecin'), gives the following as the sign of its employment, using as many dots over the note as there were to be repetitions of the sound—