Voluntary
Voluntary (from English "spontaneous") describes a piece of music (mostly for the organ ) that has been improvised or a composition of an improvisational character. The voluntary comes from the English Baroque and is comparable in its original function to the prelude . Therefore, the voluntary is not tied to a specific compositional form.
The trumpet voluntary is derived from the organ register of the same name . Even if the organ's solo register was initially meant, performances with real trumpets are also common today.
Organ Voluntaries Composers: