Method
If there is one technique that is emblematic of the tuba and euphonium’s contemporary capabilities, it is the vocal multiphonic. The vocal multiphonic has been a part of the brass repertoire since the 1800s (notably appearing in Carl Maria von Weber’s Concertino for Horn and Orchestra in 1815). The large mouthpiece and conical bore of the tuba family make it a prime target for its usage in the contemporary repertoire.
In this technique, the performer sings while simultaneously buzzing a note. A variety of different chordal sounds may be achieved. Perfect intervals and major/minor chordal tones (major/minor 3rds and 7ths) tend to be the most stable and harmonically-rich, while close and/or dissonant intervals lead to a variable amount of difference tones. In general practice, the sung note is almost always placed above the buzzed note in pitch. However, this is not a strict rule, and although more difficult to perform in general, it is certainly possible to sing below a buzzed note.
Necessary information
Since the vocal multiphonic is seen in several standard works of the solo tuba and euphonium repertoire, it is rare to find a professional-level performer that can’t perform this technique. That being said, a few guidelines are helpful in the creation of an ideal vocal multiphonic. Care must be taken to accommodate the wide vocal range of the tuba/euphonium community—for instance, many mid-twentieth century solo works utilize vocal multiphonics that were written almost exclusively for the male voice, needlessly excluding the growing population of non-male performers on the tuba and euphonium. This can be accommodated for by either limiting the multiphonic to a narrow range of pitches, or allowing for octave displacement of the vocal multiphonic.
Although many professional and advanced tubists/euphonists are more than capable of performing vocal multiphonics, it must be said that extended and/or highly active multiphonics may be difficult for some to perform. Extremely florid sung phrases may also not sound clearly, given the low range of the instruments. Additionally, combining sung and buzzed lines that are highly independent from one another may become exponentially difficult to perform, especially for those unused to such figures.
Another major guideline to follow when writing vocal multiphonics is a consideration of the relative dynamics of the technique. Because of the interference caused by the buzzing lips and the nature of the instrument itself, a typical vocal multiphonic must be sung at a louder relative volume than the buzz in order to be heard at an equal dynamic level on the bell end of the instrument. When done for too long, this can lead to fatigue, and even physical harm on behalf of the performer. For this reason, sustained vocal multiphonics often work best when written at a medium-to-low dynamic, and when a louder dynamic is required, shorter durations work better than longer durations.
Notation
The convention for notating vocal multiphonics is to use either diamond shape or X-head noteheads for the sung component. This has been the standard since the earliest uses of the technique in the solo repertoire (particularly in William Kraft’s Encounters II for tuba and James Curnow’s Symphonic Variants for euphonium), and as such is instantly recognizable as a vocal multiphonic to the professional tubist and euphonist. If an alternate notation is used, it must be properly annotated. In some works, the sung portion is notated either above the staff or on a separate stave, and as long as it is made clear that the sung portions exist on the separate stave, this technique is also acceptable. This is in line with the guidelines found in Elaine Gould’s Behind Bars.
Relative Difficulty
Intermediate to Professional
Works to consider (bolded titles are particularly representative examples of this technique)
Encounters II – William Kraft
Symphonic Variants – James Curnow
Five Studies for Tuba Alone – David Reck
Concert Variations – Jan Bach
The Composer's Guide to the Tuba 