Pedal tones (or pedals) are special low notes in theharmonic series ofbrass instruments. A pedal tone has the pitch of its harmonic series'fundamental tone. Its name comes from the footpedal keyboard pedals of apipe organ, which are used to play 16' and 32' sub-bass notes by pressing the pedals with the player's feet. Brasses with abell do not naturally vibrate at this frequency.
Aclosed cylinder vibrates at only the odd members of its harmonic series. This set of pitches is too sparse to be musically useful for brass instruments; therefore, the bells and mouthpieces of brasses are crafted to adjust these pitches. The bell significantly raises all pitches in the series, particularly on the low end, while the mouthpiece lowers the higher harmonics, limiting the amount to which higher harmonics are raised by the bell. The resulting compressed set of pitches resembles a new harmonic series that includes the even members. This new series is similar to that of a stoppedconical tube, with the exception of the fundamental, which is no longer incorporated in the harmonic series.
The original fundamental resonance is not raised all the way to the new fundamental pitch, and is not used in playing. The new fundamental can be played, however, as a pedal tone. The higher resonances of the new series help the lips vibrate at the fundamental frequency and allow the pitch to sound. The resulting tone relies heavily onovertones for its perception, but in the hands of a skilled player, pedal tones can be controlled and can sound characteristic to the instrument.
Ontrombone, pedalB♭1 is frequently seen in commercial scoring but much less often in symphonic music. Notes below B♭ are called for only rarely as they "become increasingly difficult to produce and insecure in quality" with A♭1 or G1 being the bottom limit for most trombonists.[1]
Pedal tones are called for occasionally in advanced brass repertoire, particularly in that of thetrombone and especially thebass trombone. Although not frequently used, pedal tones can often be played on adidgeridoo.