The gender is a metallophone whose relatively thin keys are strung up by means of cords on bone or metal supports sticking out of the underframe, the keys hanging above tubular resonators. These sound-tubes used to be made of bamboo, in which case they were cut in such a way that a node was left to provide the right resonance wave-length in the tube. When the key suspended above the resonator is beaten, the air-column above the node vibrates in sympathy and thus reinforces the sound. Nowadays these resonator tubes are generally made of zinc for better durability (painted yellow, to resemble the original bamboo).
Pangeran Buminata (a brother of the Susuhunan Paku Buwana IV (1786-1820), ruler of the court of Surakarta), invented the trick of covering the resonators at the top but for a small opening in the centre (like certain organ registers), so it was possible to manage with shorter tubes than before, even for the lowest tones. Since the instrument could thus be manufactured as a lower-built model, this made it unnecessary for the player’s position to be elevated, so they could avoid this breach of court-etiquette and squat on the ground just like their colleague servant/musicians.
Genders come in several varieties; in Bali they form the mainstay of the ensemble. In the gamelan of Central Java, they form a trio: the multi-octave gender panerus and gender barung – the latter sounding an octave lower than the former – and the single-octave slenthem, which doubles the pitches of the lowest octave of the gender barung. Due to the fact that its keys are larger and weightier than those of the gender barung, the projection of its sound is much more pronounced. In fact, although the slenthem player usually barely hears the instrument, the audience will hear it even through the loudest passages.
The genders are played with disc-headed mallets, held loosely by the player between index and middle finger. The slenthem however, is played saron style, although with a large disc-headed mallet.
Their tones have the longest sustain in the entire gamelan ensemble – together with the large gongs; a gender tone can last for over a minute!
Due to this long sustain and the independence of the two hands, the gender is the only true polyphonic instrument in the gamelan, and good damping technique is essential, obviously.
Muting is done with the same hand with which the tone was played: on the left and right hand side with the thumb, the back of the hand or the tip of the little finger, depending on which note was previously played, and, for low tones, when one has to play in the middle register immediately after, with the elbow. Large leaps are possible, but damping may be unreliable, if not outright risky. The gender is best suited for every kind of articulation.
Slendro & pelog
Although the soloist properties of the gender are obvious, and therefore tempting, one should bear in mind that the sound of the gender family is considerably softer than any other instrument in the ensemble. The composer should be aware of this, and adjust the surrounding instrument levels accordingly.
An interesting feature of genders is that octaves (when played in unison) tend to stand out considerably; apparently the mutual reinforcement of sympathetic vibration produces a higher sound level. This effect is not as nearly so strong in the other instruments.
In general, accompaniment to gender parts should be sparse, to keep them audible. As a support in joint forces (e.g. tutti play) genders are usually inaudible, and thus should be left out, unless the composer has a social, rather than a musical goal in mind.