Megh Malhar, a raga of considerable antiquity, is associated with the rainy season, and is considered a serious and profound raga, prescribed for performance around midnight. In this sense, this raga may be considered to represent the sombre, and even awesome, facet of the advanced monsoon (July-August), in contrast with Miyan ki Malhar and other Malhar variants, which are explicitly euphoric at the onset of the rainy season (June-July), and the imminent relief from the scorching Indian summer.
Musicologist V.N. Bhatkhande, writing in the first quarter of the 20th century (Sangeet Shastra, vol. IV, L.N. Garg, Ed.,2nd ed.,1970) observed that Megh Malhar is known to, and performed by, only a few Ustads although, according to him, it was not a particularly difficult raga to master. The popularity of the raga has improved considerably since then, even if some of the ambiguities surrounding the raga still remain unresolved.
Subba Rao (Raga Nidhi, vol.III, 4th ed., 1996, Music Academy, Madras) treats Megh and Megh Malhar as two names of the same raga, and goes on to list two versions of it, along with several sub-versions. Bhatkhande lists Megh Malhar as a variety of Malhar, and uses the two names interchangeably, while also identifying several variants of the raga in vogue in his era.
There are, very clearly, two melodic entities contending for the melodic space defined by the concept of Megh Malhar. The first is the tone material taken from the pentatonic raga (S-R-M-P-n), Madhyamadi Sarang (also called Madhmat Sarang) For conceptual clarity, and pending consideration the evidence of contemporary usage, we may call this the Megh element. The second melodic entity is a looped phrase ( R-P-g-M-R) suggestive of Miya-ki-Malhar, which uses the komal (flat) Ga with andolan (oscillated treatment). This may be called the Malhar element. In contemporary usage, however, the relationship between the nomenclature and the melodic form, remains inconsistent.