Method
The use of the tuba mute is a fairly divisive topic among the tuba community. Large and difficult to hold or move quickly, the straight tuba mute is only used on rare occasions. One of the main works of the tuba orchestral repertoire, Richard Strauss’ Ein Heldenleben, calls for a mute, but this direction is sometimes ignored even among professional orchestras. The tuba mute is much more successful within solo and chamber settings, where it can serve to create a subdued tone. The euphonium has a greater access to the mute, and as such is called for at a greater rate than the tuba. Both instruments have ready access to straight mutes, while only a few bucket mutes having been manufactured over the years. There are also practice mutes, which are designed to diminish the sound as much as possible.
Necessary information
The primary issue with mutes of all kinds for tuba and euphonium is the fact that even the best mute has a tendency to create “wolf tones,” which are notes that don’t speak well or are severely out-of-tune when the mute is inserted. This has to do with the way in which the mute functions, as it is placed very far into the tuba and euphonium bell and disrupts the acoustics of the open bugle. This issue is compounded by the variety of bell shapes found among euphoniums and [especially] tubas. The result is the reliance by mute manufacturers on a “one-size-fits-all” approach, leading to a mute that is slightly ill-fitting for just about every instrument.
Placing and removing the mute is a difficult task, and is often a fairly noisy affair. Tubists with shorter arms may even have to place the instrument on the floor in order to get the bottom of the mute clear of the bell rim before insertion.
Most tuba and euphonium mutes are made of metal, but this isn’t a hard and fast rule. There are a few different popular lines of tuba/euphonium mutes that are made of wood or fiberglass, for instance.
Although most professional tubists and euphonists will have access to at least one mute, this isn’t a guarantee. It is even less likely that the tubist/euphonist will have a practice mute that is suitable for their instrument.
Notation
For ordinario usage, the standard conventions for mute usage are more than sufficient. For anything more complex than that, any directions that are consistent and get the point across are advisable. It is possible to achieve fractional insertions of the mute, but it must be kept in mind that holding the mute in the air is both very tiring and very awkward. If that is required, though, this can be achieved by a simple fraction that indicates the amount of the mute is to be inserted into the bell (i.e., ½ mute, ¾ mute, and so on). Indeed, this is only present in one of the works listed below (the double belled euphonium work by Liza Lim), and in that case, the performer has an assistant that helps with muting.
Relative Difficulty
Intermediate to Professional
Works to consider (bolded titles are particularly representative examples of this technique)
Durations III – Morton Feldman
The Green Lion Eats the Sun – Liza Lim
center unmoored in the presence of infinite fringes – Colin Tucker
Polis for Unaided Tuba – Brent Dutton
The Composer's Guide to the Tuba 