There are a selection of keyboards available to the composer for orchestral use, both solo and as an orchestral instrument. We will write of two here, the Piano, and Harpsichord. Although the Harpsichord is considered more at home in music written in the baroque period, it is enjoying something of a renaissance in the modern orchestra, as composers revisit this instrument, and its unique characteristics.
The Piano remains undimmed in its history, and has been used for a considerable number of works from its inception, to the present day. Construction techniques have improved with more consistency in the build, and this gives the composer a chance to expand further, music written for this instrument. The Piano is equally at home in the orchestra as solo or part of the ensemble, and it's unique tone can be easily identified in either role. In 19th, and 20th Century music, particularly from Russian composers, the piano was used frequently in orchestras and clever use was made of it as a colour instrument. As a solo instrument, the Piano has few peers, and it can, in the hands of a virtuoso, invoke a considerable range of emotions in the listener.
There is so much literature available for the Piano in external resources, that we'll give a brief summary here, and encourage visitors to explore more widely in publications, and the internet, for specialised information.
The Piano has many variations of construction, from 12ft Grand Pianos to desktop spinnets, and uprights. Generally speaking, a concert grand Piano has 88 keys, and produces sound with a hammer action, striking strings. In the range of a piano from lowest pitch to highest, there are different combinations of strings, with lower tones generally using 1 string per key, going to 2 strings per key, then three. As the player strikes a note, a damper, normally sitting on the string, rises, and the felt covered hammer strikes the string, producing a vibration, and sound. If the player lifts his finger from the note, the damper sits on the string again, and stops the vibration, but by using a pedal, the player can sustain the sound for longer. The Piano string, once struck, begins to die away immediately, unlike blown or bowed instruments, which can sustain a note as required by the composer. If the player wishes to attempt some degree of sustaining a note, then he or she uses a tremolo to do so.
The dampers can be lifted and help up by use of a pedal, as previously described, but the composer can also make use of the rich overtones of a piano asking the player to depress keys silently, and hold the damper pedal down. Other instruments producing sound then provoke a resonance or overtone from the undampered piano strings, adding a new dimension to the music. This effect has been used extensively in film music to add a surreal or sinister effect, and used sparingly, is a useful musical device in the composer's toolbox.
Played softly, as an orchestral instrument, the piano has a unique characteristic that sits well with woodwinds, and brass. It sits a little less well with strings, but if used carefully, can add an interesting tonal element to string sections. As an orchestral instrument, the Piano is particularly suited as a melodic device, for short or medium passages, and as a 'question and answer' variation with woodwinds, and Horns, to name just two examples.
The Harpsichord produces its tone by the action of a quill plucking a string. The quill is attached by means of a device called a jack, which is raised when the player presses a key. As mentioned above, the Harpsichord is an old instrument that has enjoyed a resurgence in popularity, and is being used more often by modern composers, particularly when writing for film, outside of generic action scores.
The instrument may have 1 or 2 keyboards, or manuals, with some larger instruments using an additional 3rd manual, or a pedal clavier. Each keyboard has one or more sets of strings that are directly activated by jacks specific to a keyboard, and on modern instruments, the upper manual has 2 sets of strings by default. These sets of strings, called stops, or registers, are controlled by foot pedals, or hand drawn levers. On the modern Harpsichord it's possible to use a connector for more than one set of strings, and have multiples playing from one register.
The Harpsichord has no dynamic control, save the stops, pedals, and levers, and the multiple use of these devices, with the player doubling sets of strings in order to emulate coarse dynamic changes. With it's very delicate sound, the Harpsichord should be written for with care by the composer, as it can get lost among instruments who are scored too loud, or in too great a number.