Bifara
An organ stop with pairs of slightly detuned pipes that create a wavering tone, serving as an alternative to the tremulant.
What it means
The bifara is an organ stop in which each note sounds from two pipes of the same pitch that are slightly detuned from each other. This tiny difference produces beating, a gentle, wave-like fluctuation in loudness that gives the tone a lively, vibrating quality.
The name derives from the Latin word for "two-piped," directly describing the stop's construction from pairs of pipes.
Musical use
Historically, the bifara served mainly as a tonal alternative to the mechanical tremulant, which periodically varies the wind supply to create a shimmer. While the tremulant works through a mechanical device, the bifara's wavering effect arises purely from the detuning of the pipes themselves.
It should be distinguished from the tremulant as a separate mechanical component, and from the voix céleste, a related, similarly wavering stop usually used in a different tonal context, such as Romantic organs.
Performance practice
When registering an organ with the bifara, use it deliberately where a shimmering, atmospheric sound is wanted, such as in calm, meditative passages. Combine it sparingly with other stops so the subtle wavering effect remains audible.