4.5 Mutes
165
Fig. 4.58 Excerpt from the first trumpet part in Petrouchka by Igor Stravinsky (1947 Version).
Reproduced by permission of Boosey & Hawkes Music Publishers Ltd
the sound output completely, although the role of a ‘practice mute’ is to reduce the
amplitude of the radiated sound to a level at which neighbours are not disturbed.
All mutes modify both the loudness and the timbre of the sound, and the timbral
change is usually the primary motivation for using a mute in performance. A muting
instruction does not necessarily imply that the passage will be played quietly: the
dramatic timbre of muted brass instruments played fortissimo has been exploited by
many composers, including Igor Stravinsky (Fig. 4.58).
With the exception of the instruments with toneholes discussed in Sect. 4.4, on
which mutes are not normally used, all the sound output of a brass instrument
emerges through the bell. Brass instrument mutes are devices which modify the
way in which sound waves are reflected and radiated when they reach the bell. In a
comprehensive survey of the acoustical and musical properties of brass instrument
mutes, Sluchin and Caussé (1991) draw a useful distinction between internal mutes
which penetrate into the bell and external mutes which are held outside the bell. In
the following sections, we discuss two types of internal mute, the straight mute and
the Harmon mute, and also the external mute known as the plunger.
4.5.1 Straight Mutes
A typical trumpet straight mute is illustrated in Fig. 4.59. The mute is a thin-walled
hollow metal vessel whose only opening is a circular hole at the narrow end. Three
thin strips of cork, visible in Fig. 4.59a, act as spacers between the outer surface of
the mute and the inner surface of the bell when the mute is inserted as shown in
Fig. 4.59b.
The mute shown in Fig. 4.59 has a complex profile designed to match the inner
profile of a trumpet bell. The cork spacers maintain a gap of a few millimetres
between the outer surface of the mute and the inner surface of the bell. The sound is
radiated through this narrow channel, which also allows the mean flow to escape.
The most basic design of straight mute is simply a truncated cone closed at the
wide end, as illustrated in Fig. 4.60.
The effect of the straight mute shown in Fig. 4.60 on the input impedance of
a Conn 8H tenor trombone is illustrated in Fig. 4.61. In Fig. 4.61a the slide is in
first position (fully retracted). Comparison of the blue curve (without mute) and
the red curve (with mute) shows that the insertion of the mute has almost no effect
on the frequencies or amplitudes of the impedance maxima between 100 Hz and
165
Fig. 4.58 Excerpt from the first trumpet part in Petrouchka by Igor Stravinsky (1947 Version).
Reproduced by permission of Boosey & Hawkes Music Publishers Ltd
the sound output completely, although the role of a ‘practice mute’ is to reduce the
amplitude of the radiated sound to a level at which neighbours are not disturbed.
All mutes modify both the loudness and the timbre of the sound, and the timbral
change is usually the primary motivation for using a mute in performance. A muting
instruction does not necessarily imply that the passage will be played quietly: the
dramatic timbre of muted brass instruments played fortissimo has been exploited by
many composers, including Igor Stravinsky (Fig. 4.58).
With the exception of the instruments with toneholes discussed in Sect. 4.4, on
which mutes are not normally used, all the sound output of a brass instrument
emerges through the bell. Brass instrument mutes are devices which modify the
way in which sound waves are reflected and radiated when they reach the bell. In a
comprehensive survey of the acoustical and musical properties of brass instrument
mutes, Sluchin and Caussé (1991) draw a useful distinction between internal mutes
which penetrate into the bell and external mutes which are held outside the bell. In
the following sections, we discuss two types of internal mute, the straight mute and
the Harmon mute, and also the external mute known as the plunger.
4.5.1 Straight Mutes
A typical trumpet straight mute is illustrated in Fig. 4.59. The mute is a thin-walled
hollow metal vessel whose only opening is a circular hole at the narrow end. Three
thin strips of cork, visible in Fig. 4.59a, act as spacers between the outer surface of
the mute and the inner surface of the bell when the mute is inserted as shown in
Fig. 4.59b.
The mute shown in Fig. 4.59 has a complex profile designed to match the inner
profile of a trumpet bell. The cork spacers maintain a gap of a few millimetres
between the outer surface of the mute and the inner surface of the bell. The sound is
radiated through this narrow channel, which also allows the mean flow to escape.
The most basic design of straight mute is simply a truncated cone closed at the
wide end, as illustrated in Fig. 4.60.
The effect of the straight mute shown in Fig. 4.60 on the input impedance of
a Conn 8H tenor trombone is illustrated in Fig. 4.61. In Fig. 4.61a the slide is in
first position (fully retracted). Comparison of the blue curve (without mute) and
the red curve (with mute) shows that the insertion of the mute has almost no effect
on the frequencies or amplitudes of the impedance maxima between 100 Hz and