【Melody】 , 【air】 ,  【tune】  all denote a clearly distinguishable succession of rhythmically ordered tones.

【Melody】 stresses the sweetness or beauty of sound produced by such an arrangement of tones. It also commonly suggests expressiveness or moving power and a carefully wrought pattern. Technically, as applied to complex musical structure,  【melody】  implies a contrast to harmony; it designates that kind of musical beauty produced by a continuous series of tones in one or more of the voice parts, in distinction from that produced by simultaneously sounded tones in all the voice parts.

【Air】 is applied technically to the dominating 【melody】 , usually carried by the upper voices (as in a chorale or part-song). In more general use  【air】  is often applied to an easily remembered succession of tones which identifies a simple musical composition (as a song, a ballad, or a waltz) and which is more commonly and more precisely called  【tune】 ; thus, one may refer to the  【air】 , or the  【tune】 , of a song.

【Tune】  is also applied to the musical setting of a text (as a ballad, psalm, or lyric) <a hymn  【tune】 >  and to a simple composition whether unison or harmonized.