> Strictly speaking, this system is defined only for notated music. We cannot identify the interval between two notes just by listening. However, there are a se

> Strictly speaking, this system is defined only for notated music. We cannot identify the interval between two notes just by listening. However, there are a set of common conventions for notating music that typically make it possible to guess the correct letter-name interval, merely by listening. I think he means that when you hear a tritone you cannot say for sure whether it's an augmented fourth or a diminished fifth - the notation could technically be written either way. But usually, the "set of common conventions" that he mentions will make one "more correct" than the other.