Na'vi express their innermost feelings through quiet improvisational singing (way), usually when alone in the midst of the forest. Both men and women perform this genre, usually when wandering by themselves, and often as appreciation of the beauty of their world. Eywa, the Hometree, and mates are the most common audience for this type of musical expression.
These songs may take the form of a slow, mournful, undulating melody with very little variation in pitch, or a livelier sort of warbling. Some Na'vi sing using words to express their sentiments; others leave the sentiment to be expressed through their melodies. These seemingly random sounds, known on Earth as “vocables,” are non-lexical or non-semantic syllables, like “fa la la,” which have no intrinsic meaning but are easy to sing. Some elder Na'vi and linguistic researchers theorize that many of the vocables used during personal songs may be derivations or mutations of old Na'vi words, or perhaps even remnants of a language that predates the Na'vi. One example would be the vocables “te-la-ni,” which is often sung repeatedly. Some theorize that this is a derivation of the word txe’lan or “heart.” Another common vocable, “tra-la,” resembles the word Utralä, “the tree.”
Pandorapedia - Personal Songs article