Scales such as the pentatonic scale may be considered "gapped" relative to the diatonic scale. Three-note stacks based on diatonic and pentatonic scales are also, strictly speaking, tone clusters. Musicians traditionally tune this harp using pentatonic scales. He also employed blues and minor pentatonic scales. Jazz music commonly uses both the major and the minor pentatonic scales. Blackfoot music most often uses anhemitonic tetratonic or pentatonic scales. This is followed by two guitars, one of which plays a pentatonic scale riff. Pentatonic and hexatonic scales are very common scales across Africa. It makes extensive use of pentatonic scales and mimics traditional Indonesian melodies. In addition to using modal harmonic relationships, heavy metal also uses "pentatonic and blues-derived features". This minor pentatonic contains all three tones of an A minor triad. Non-Western music, particular that built on pentatonic scales, is largely tuned using just intonation. The music is largely modal, beginning with pentatonic (both major and minor) scales. Pentatonic scales were developed independently by many ancient civilizations. Before 1940, minor and pentatonic scales were predominant in Trot.