Especially when the distance between adjacent partials is large, there is a gap in which the tuba refuses to sound. As the player approaches the cusp slowly from either side via lip glissing, the instrument struggles to phonate, eventually leaping up or down to the next partial. The sound of the struggle followed by the jump is similar to that of a vehicle stalling out, especially if the tubist cuts off before the next partial locks in. It should be noted that the latter, in particular, is difficult to do, owing to the precariousness at the cusp (i.e., the likelihood of suddenly and unpredictably locking into the next partial).
Split tones are produced by forcing the tuba to phonate between partials, resulting in the illusion of a diad multiphonic. The technique is inherently unstable and will likely require considerable practice to control. Timbres vary greatly depending on register: between lower partials, the sound is highly unstable with a rumbling, intensely rhythmic quality; between higher partials, the sound is much more focused and of clearer pitch content.
It is possible to approach the split tone like a gliss cusp (i.e., via embouchure), only in this case, one attempts to hold the phonation between the two partials. It is also possible to enter directly into a split tone. However, in either case there is a degree of insecurity. While it is possible to lock into the diad, there is always the risk of jumping suddenly to one of the two partials. This may be reduced through practice.
Pitch range. Same as ordinario. It should be noted that there is a modest degree of inward microtonal convergence in the partials, as neither is allowed to fully settle in to its proper resonance.
Dynamic range. Register-dependent. For lower split tones, the instrument peaks around mf; for higher ones, at f or even ff. It is generally possible to play split tones at a variety of dynamics and also to swell and/or decay while sustaining them.
Practice tip(s). We have found that the best means of playing split tones is to decouple fingering and embouchure, such that one fingers the appropriate valve configuration for the desired partials and aims half-way between the two with embouchure (e.g., if sustaining a split tone between C2 and G2, an E-quarterflat2 embouchure is recommended). A comprehensive chart of fingering and embouchure combinations and their corresponding split tones will be included as an appendix to a later draft of this catalog.