Method
Due to the acoustical nature of the tuba and euphonium, it is possible to move rapidly between adjacent partials by subtly changing the embouchure. Although this technique is often difficult for less experienced performers, it is often included as part of a standard warmup and maintenance routine for tubists and euphonists.
Necessary information
Although technically possible between the lower partials, the lip trill is most effective between partials that are closer together in pitch (starting around the 4th partial and ascending). As noted above, this technique is also somewhat difficult for performers who have not thoroughly practiced the technique. The speed between partials in the trill may be variable, with higher rates of speed being slightly more idiomatic. The lip trill, especially at rapid speeds, is considered an advanced technique.
Notation
There are a few different standardized means for notating a trill, with the most common being a combination of the abbreviation “tr” and a wavy line across the area in which the trill is called for (if needed). The thickness and amount of “waves” present in the line may be varied in order to indicate a variable trill speed. When calling specifically for a lip trill, a simple text declamation above the trill will suffice. It may also be helpful to indicate either as a grace note or as a parenthetical notehead the note and direction in which the desired lip trill is moving.
Relative Difficulty
Advanced to Professional
Works to consider (bolded titles are particularly representative examples of this technique)
Concerto for Euphonium – Robert Jager
Solo Tuba Music – Cort Lippe
Midnight Realities – Morgan Powell
The Composer's Guide to the Tuba 