Pelog

Pelog is one of the two principal tuning systems used in traditional Indonesian gamelan music, the other being slendro. It consists of seven pitch levels per octave (a heptatonic scale), but the actual pitches employed in a given gamelan are not fixed; ensembles select subsets of the seven tones for a piece, and tunings vary between ensembles. The intervals between adjacent notes are uneven, giving pelog a distinctive, non-tempered character that differs from the more regular spacing of slendro.

In performance, melodies often use five or six of the seven pelog pitches, with the remaining tones reserved for ornaments or cadential gestures. The choice of tones and melodic direction is influenced by pathet, a modal system that defines permissible scale degrees and their emotional functions.

Pelog is widely used in Java and Bali, with regional variations in scale and tuning. Instruments such as saron, gender, bonang, and gambang, along with gongs, are typically tuned to the same pelog collection within an ensemble, ensuring cohesion of pitch relationships. Balinese gamelan often deploys several pelog variants alongside slendro, while Central Javanese ensembles use pelog in a number of repertories.

Compared with slendro, pelog has a more diverse, irregular pitch geometry, which contributes to its distinctive timbre and melodic possibilities. Because pelog scales are not standardized in the same way as Western scales, performances are commonly tuned to match a specific ensemble rather than a universal pitch set.