"Melody type" is a fundamental notion for understanding a nature of Western and non-Western musical modes, according to Harold Powers' seminal article "Mode" in the first edition of the New Grove Dictionary of Music and Musicians (Powers 1980, 12:376–77, 379, et passim).
One of the challenges of folk song research, of course, is to find all the variants of the tune and to try to trace the family relationships.
Here the melody type is similar to a church mode: a scalar configuration with a preferential order of tones.
Melody types are found mostly in the music of ancient peoples—the Greeks, Hebrews, and others—and of Eastern peoples—the Arabs, Persians (Iranians), Indians, and others.
For...example... raga.In most cases, these melody types are associated with extra-musical implications, particularly emotions (see Indian rasa, for instance).