IPA: /ˌʌn.məˈloʊ.di.əs.nəs/
KK: /ʌnˌmɛləˈdoʊiəsnəs/
The quality or state of lacking a pleasant sound or melody.
The unmelodiousness of the noise made it hard to enjoy the music.
Unmelodiousness → It is formed from "un-" (meaning not), "melodious" (from Greek "melodios", meaning having melody), and "-ness" (meaning the state of being). The word describes the state of not being melodious or lacking melody.
Think of 'not' ('un-') having 'melody' ('melodious') — that's why 'unmelodiousness' means the state of lacking melody.