I am building a conlang, which is very likely going to be an isolating language. As such, I decided to make it a tonal language.
But there is a problem. This language is to be sung very often, so using pitch as a suprasegmental would compromise understanding lyrics.
So instead of tones, I decided to pick another kind of suprasegmentals. Candidates in my mind were:
Phonation, e.g. Voiceless [ḁ] / Breathy [a̤] / Modal [a] / Creaky [a̰].
Nasalization, e.g. Oral [a] / Nasal [ã].
Tongue root position, e.g. Advanced [a̘] / Relaxed [a] / Retracted [a̙].
I took the third option. Yet I doubt any natural language does this. Is there any?