Pelog is one of the two essential scales of gamelan music native to Bali and Java, in Indonesia. In Javanese the term is said to be a variant of the word pelag meaning "fine" or "beautiful". The other, older, scale commonly used is called slendro. Pelog has seven notes, but many gamelan ensembles only have keys for five of the pitches. Even in ensembles that have all seven notes, many pieces only use a subset of five notes.
Since the tuning varies so widely from island to island, village to village, and even gamelan to gamelan, it is difficult to characterize in terms of intervals. One rough approximation expresses the seven pitches of Central Javanese pelog as a subset of 9-tone equal temperament. An analysis of 27 Central Javanese gamelans by Surjodiningrat (1972) revealed a statistical preference for this system of tuning.
As in slendro, although the intervals vary from one gamelan to the next, the intervals between notes in a scale are very close to identical for different instruments within the same Javanese gamelan. This is not the case in Bali, where instruments are played in pairs which are tuned slightly apart so as to produce interference beating. The beating is ideally at a consistent speed for all pairs of notes in all registers. This contributes to the very "agitated" and "shimmering" sound of gamelan ensembles. In the religious ceremonies that contain gamelan, these interference beats are meant to give the listener a feeling of a god's presence or a stepping stone to a meditative state.
The notes of the slendro scale can be designated in different ways; In Java, one common way is the use of numbers (often called by their names in Javanese, especially in a shortened form. An older set uses names derived from parts of the body. Notice that both systems have the same designations for 5 and 6.
Although the full pelog scale has seven tones, usually only a five-tone subset is used (see the similar Western concept of mode). In fact, many gamelan instruments physically lack keys for two of the tones. Different regions, such as Central Java or West Java (Sunda), use different subsets. In Central Javanese gamelan, the pelog scale is traditionally divided into three pathet (modes). Two of these, called pathet nem and pathet lima, use the subset of 1, 2, 3, 5, and 6; the third, pathet barang, uses 2, 3, 5, 6, and 7. The remaining two notes, including 4 in every pathet, are available for embellishments on most instruments, but they do not usually appear on gendér, gambang, or interpunctuating instruments.
In Bali, all seven tones are used in gamelan semar pegulingan and gamelan gambuh. All seven tones are rarely heard in a single traditional composition. Like in Java, five-tone modes are used. There are three modes, selisir, tembung and sunaren. Gamelan gong kebyar instruments have five keys in the pelog selisir mode (heard in the audio example above). Unlike Java, there are only five names for the notes, and the same five names are used in all three modes. The modes all start on the note named ding, and then continue going up the scale to dong, deng, dung and dang. This means that the same pitch will have a different name in a different mode. The modes are arranged as follows:
^ abc"The representations of slendro and pelog tuning systems in Western notation shown above should not be regarded in any sense as absolute. Not only is it difficult to convey non-Western scales with Western notation, but also because, in general, no two gamelan sets will have exactly the same tuning, either in pitch or in interval structure. There are no Javanese standard forms of these two tuning systems." Lindsay, Jennifer (1992). Javanese Gamelan, p.39-41. ISBN 0-19-588582-1.