EUPHONY. A pleasant, harmonious quality in SPEECH. The perception of such a quality is partly physiological (soft, flowing, blending sounds are generally considered pleasanter than harsh, jangling, discordant sounds) and partly cultural (people tend to like sounds that they have been led to like). In English, euphony is often associated with long vowels, the semi-vowels or glides /j, w/, and the consonants /l, m, n, r/. All of these occur in the opening verse of Gray's ‘Elegy Written in a Country Church-Yard’ (1751):The Curfew tolls the knell of parting day,
The lowing herd winds slowly o'er the lea,
The plowman homeward plods his weary way,
And leaves the world to darkness and to me.
Euphony can be achieved through the skilled use of a language's rhythms and patterns together with positive associations shared by performer and audience. These associations may relate to sound (preferred voice qualities and accents), allusion (oblique references to favoured or familiar poems, songs, etc.), and experience (bringing in positive images like spring, morning, youth, hope, love, and dreams). There may be agreement that X is euphonious and Y cacophonous, but people may differ as to just how and why this is so. Euphony in the sense of a greater ease in saying and hearing sounds has been cited as important in grammar and word-formation: as the reason for an apple rather than *a apple, Aren't I? and not *Amn't I?, tobacconist and not *tobaccoist, impossible rather than *inpossible or *unpossible, and calculable rather than *calculatable. In matters of this kind, however, analogy, convention, and phonology appear to be more significant factors.

eu·pho·ny / ˈyoōfənē/ • n. (pl. -nies) the quality of being pleasing to the ear, esp. through a harmonious combination of words. ∎  the tendency to make phonetic change for ease of pronunciation.DERIVATIVES: eu·phon·ic / yoōˈfänik/ adj.eu·pho·nize / -ˌnīz/ v.

euphony XVII (once XV). — F. euphonie — late L. euphōnia — Gr. euphōníā, f. eúphōnos well-sounding, f. EU- + phōnḗ sound, voice; see -Y3.
Hence euphonious XVIII.