Schwellton
A swelling and diminishing note.
What it means
A Schwellton is a sustained note that begins softly, grows, and diminishes again. The term is the German equivalent of the Italian messa di voce and designates the same thing. A precondition is an instrument or a voice that can change the note while it sounds — singing voice, wind and string instruments. Harpsichord and organ cannot do this; the organ helps itself with the swell box, in which shutters in front of the pipework open and close the sound steplessly.
In the notation
The Schwellton is indicated by two hairpins placed against each other over a long note. In music of the seventeenth and eighteenth centuries the marking is often absent, although the execution was expected; there, knowledge of style decides. With organ music using the swell box, indications for the pedal are additionally given.
Musical use
The Schwellton gives a single note an inner movement and thereby weight. It suits beginnings that come out of silence, climaxes of a phrase, and endings that fade away. In vocal pedagogy it is at the same time a basic exercise, because breath control and register balance show themselves in it. In the orchestra, the shared swelling of a whole section is an effective device but demands coordination, so that everyone takes the same course.
Performance practice
Divide the note mentally into two equal halves and plan the climax precisely. Begin with little air or bow but full support; a powerless beginning later forces you to push. Take care that pitch and tone colour stay the same, and check with a recording. With string players the intensification arises from arm weight and bow speed together, with wind players from air flow, not from lip pressure. In ensemble, agree on the course and the peak point.
Bear in mind that a shared Schwellton in ensemble demands agreement: everyone must take the same peak point and the same course, otherwise a restless surface arises instead of a movement. Agree on both explicitly. On the organ, the swell box takes on this task; check the pedal and plan its use like a voice.