Which is NOT true about vocal techniques of throat singing

Прочитайте текст. Запишите в поле ответа цифру 1, 2, 3 или 4, соответствующую выбранному вами варианту ответа.

Which is NOT true about vocal techniques of throat singing?

1. Scientists cannot have a mutual definition.
2. It is compared with an overtone.
3. It is characterized by different tones appearing at the same time.
4. Throat singing is explained by special harmonic skills.