Split tones are generated by modifying the lips in a way that allows for multiple harmonic partials to be activated through the buzz. This is primarily achieved by allowing the buzz to be loosened to the point of moving to the lower partial of a particular harmonic series. However, instead of allowing the lips to settle on the lower note, the performer instead holds the lips at the “break point” between the two partials. In doing so, a dyad multiphonic is created. Split tones are distinct from vocal multiphonics in that the multiple tones of the multiphonic are created with the lips, rather than a combination of the lips and vocal cords.
Split tones are generally more stable in partials 2-5 of the tuba and euphonium, as these partials contain a copious amount of acoustical space between adjacent notes. Of particular interest is the fact that the tuba and euphonium contain a “false” partial between the 1st and 2nd partials, which can be used in a split tone like any other true partial.
Split tones above partial 5 are certainly achievable, but are much less stable and more difficult to perform than lower STs. At this range, the method for performing split tones approaches that of overpressurization, a closely related yet distinct contemporary technique.
Performing split tones instantaneously takes a lot of control, and must be practiced rigorously in order to be achieved consistently. This is more of an issue for the performer, but knowledge of that fact is crucial in writing efficient split tones.
Split tones can be performed from a soft to a loud dynamic, although the mechanisms of the technique are more stable from medium-soft to medium-loud dynamics. It is possible to crescendo/decrescendo while performing split tones, as well.
Most importantly, it is vital to understand that split tones are still considered by an appreciable portion of the brass community to be a playing defect, rather than a contemporary technique. This belief is rooted in the fact that the split tone (which is a controlled effect) is linked very closely in many players’ minds to double buzzing (an uncontrolled effect), the latter of which is a common issue with young brass players. Additionally, some performers are physically incapable of performing this technique. As a result, this technique still has a bit of a stigma attached to it, although that is slowly changing with each passing generation of brass players. For the moment, though, this is a technique best used when the composer is aware that the intended performer is comfortable with the technique. Although a vital component of the contemporary repertoire, it is still very much a technique for advanced players almost exclusively.
For more information about split tones, the author highly recommends trombonist Matt Barbier’s manual Face|Resection. Mr. Barbier is one of the most skilled performers of split tones, let alone of the trombone, and his manual goes into far greater detail on this important technique.
The most common method for notating split tones is by notating a dyad, and then enclosing the lower note with parentheses. This correlates to the way that the technique is perceived by the performer: to perform a split tone, it is common to visualize the dyad as building down from the root note. Additionally, it is very helpful to notate a ratio above the dyad that explicitly indicates the partials to be split (as seen in the musical examples). This can also be seen and heard very clearly in the Works to consider for this technique, particularly in the case of the work by composer Ray Evanoff; in his composition, the split tones (notated specifically for the Eb tuba), are notated both as a common notehead dyad and as a ratio of the partials.
Works to consider (bolded titles are particularly representative examples of this technique)
19 E. Main St., Alhambra, CA 91801 – Nicholas Deyoe
category – Charlie Sdraulig
Helpless Before a Creature Which Defies Physical Laws and Communicates Only Through Death – Ray Evanoff
 Matt Barbier, “face|resection,” face|resection, accessed January 3, 2019, http://www.mattbarbier.com/face-resection.php.
Ex. 8 Euphonium Recording Download
Ex. 8 Eb Tuba Recording Download