Pitched percussion can best be described as something that can be struck that has a definite pitch. Orchestras use a fairly small variety of pitched percussion instruments in a basic instrument list, but this should not dissuade the composer from experimenting with other pitched percussive sound sources.
The "standard" pitched percussion instruments, when orchestrated for, provide a useful section for added colour in a score, and they should be best considered for this purpose, aside from any music written specifically as a solo performance.
We list 4 here, but the composer is encouraged to explore more detailed sources for more specific information about others.
The xylophone is an instrument with a unique and obvious sound produced by the performer striking horizontal wooden blocks or keys laid in lengths. The keys are cut to a defined length to produce a defined pitch, and organised in a piano keyboard system, including semitonal increments. Somewhat curiously, the xylophone shares a feature in common with that of the piccolo, that is a penetrative ability to cut through any section, or orchestration, no matter how loud, in it's upper registers. The composer should consider this when writing for the xylophone, and dynamics may require marking below that of other instruments to achieve a sensible balance between the xylophone and the rest of the orchestra.
The xylophone is normally played with up to 4 mallets, generally 2 in each hand, depending on the notated requirements, and these mallets can be of varying hardnesses, or construction, enabling the performer and composer the choice of a wide variety of tones and dynamics. The performer is capable of playing with mixed mallets, that is soft mallets in one hand, and hard in the other, but the composer must make sure the indications for mallet type are clearly marked to avoid confusion, or incorrect interpretation by the performer, and conductor.
An important note for the composer is the almost immediate delay time of the xylophone. Unlike most other instruments, the sound of a xylophone key being struck fades almost immediately, even with some instruments constructed with resonation tubes of steel vertically positioned under each key. A xylophone roll to sustain some sort of sound should be used very carefully indeed, as the sound of each stroke of the roll can be heard distinctly, and could often be heard as comic, or ludicrous.
In the lower register of the xylophone, the sound is darker and less brittle than the upper register, which when struck, can be akin to the sound of breaking a stick, or snapping a piece of hardwood.
If the xylophone is the upper or soprano instrument of the wooden keyed pitched percussion section, then it's lower relation is the marimba. Unlike the more brittle quality of the xylophone, the marimba is softer, and less penetrative in tone. It's played with soft mallets usually made of yarn, and it's tone can be quickly covered by other instruments, so the composer should take care to keep the accompaniment thin, and soft, when writing for the marimba. With it's gentle nature, and lack of power or bite, the marimba is less often seen in arrangements than the xylophone, but still offers a warmer sound colour than the xylophone when used well. The unique tone of the marimba is a surprising, and often pleasing sound colour in an arrangement, no matter how little it's used. Writing mallet rolls for marimba is a safer proposition than for xylophone, as the performer will roll by default any note longer than a crotchet, or quarter note, unless otherwise specified in the score. (and it would make no sense at all for the composer to write minims, or half notes, for the marimba player, and indicate he's not to roll the note.)
Like the xylophone, the marimba player can use up to 4 mallets to play, but care should be taken that the requirement for multi mallets is for chordal work, and not musical lines or phrases that required rapid pitch changes over the keyboard. It's also consider poor writing to mix chords and more adventurous melodic lines at the same time, unless scored for 2 marimbas, giving each a defined role.
The glockenspiel, also known as orchestral bells, is generally considered as being played 2 octaves above written. With a clear tone, and in the upper registers, a bell like quality, the glockenspiel is instantly recognisable when played in the orchestra. Although it can be played with brass mallets, it's more often likely to be played with rubber mallets, as the tone can be sometimes piercingly overpowerful, and too metallic. The glockenspiel is definitely a tone colour instrument and should be used more for effect by the composer, than regular inclusion in an orchestration. Played rapid sequences on the glockenspiel dulls the effect for the listener, as the pitch and tone, sitting so far up the harmonic scale, tends to blur, and become indistinct in pitch.
As the glockenspiel is at one end of the pitched bell-like orchestral percussion, so the tubular bells are at the other end. Of metal construction, the tubes, or bells are mounted in a standing rack, each one suspended with wires, and all bells go down through a rack which is lined with felt. This is the damper with which the performer can instantly stop the rich and prolonged resonance the tubular bells create when struck. The performer usually strikes the crown, or top of the bell with a wooden or hard plastic hammer, or mallet, but felt covered mallets are also used to produced a muffled, almost eerie tone.
Like the other "keyboard based" pitched percussion instruments, the tubular bells are arranged in a semitonal configuration, similar to an upright piano keyboard, and generally cover 2 octaves. Unlike other pitched percussion, the tone of the tubular bells is less defined, and a sense of pitch can be more felt, than clearly heard, as each bell has complex overtones, that mingle and mix to "confuse" the sense of pitch placement. It would be useful for example, for the composer to visit several concerts featuring music written for the tubular bells, and sit in different parts of the concert hall, focusing on the confused sense of pitch the tubular bells eminate, dependent on distance and reflections from surrounding surfaces.
As a substitute for full sized church bells, the tubular bells do a credible job within a concert environment, but lacking in real power. Like the glockenspiel, tubualr bells are a colour instrument, and should be used sparingly and with careful consideration, to maximise the effect.