The Na'vi people have no indigenous musical theory; they do not analyze or codify their musical creations. Like many aboriginal cultures, they believe that their music was given to them by Eywa, the great spirit of Pandora. Songs come to the Na'vi through dreams, while wandering alone, or while linked with the consciousness of Pandora through their queues. Na'vi do not claim ownerships; the songs belong to all. After the establishment of communication with the Na'vi, Terran researchers came to the moon to observe and investigate Na'vi life. Xenomusicologists came along on later excursions to Pandora and, through the avatars, began to analyze the musical performances, musical instruments, song structures, and musical function. What they found was in some ways typical of Earth’s aboriginal cultures (the predominance of vocal music and drums), but they also discovered some significant differences such as the use of numerous different scale structures, many different textures, and divergent yet simultaneous singing styles. The Na'vi categorization system groups songs by function (personal, social or ritual) and performer (men, women, children, or all).
The Na'vi do not analyze their music; they just perform it in the same manner that was given or taught to them. The theoretical information given here is the result of observation and analysis by xenomusicologists. There has been no confirmation of musical theories by the Na'vi themselves. Although they are highly creative in their approach to music, they do not recognize any theoretical basis other than Eywa and are reluctant to discuss their music with outsiders who do not See. An Earth-style musicological analysis would make absolutely no sense to them, and they believe the study of music to be a waste of time.
Source
Pandorapedia - Na'vi Music Theory article