In Indian Classical Music, the Madhyam swar (Ma) is considered as the Adhva Darshak swar. The guiding swar which decides the time of singing the raga and which alters the raga swaroop is called the ‘Adhva Darshak swar’.
‘Madhyam’ swar has a special importance in Indian classical music in context with raga samaya (time). It plays a guiding role in raga vibhajan (division) according to the time of singing the raga. Therefore Madhyam is known as Adhva Darshak Swar. ‘Adhva’ means path/direction and ‘Adhva Darshak’ means the one who shows the path/direction. Eg : If Re Dha are komal (flat) and Ma is shudha then these Sandhiprakash ragas are pratahkaleen (to be sung early in the morning,) and if Re Dha are komal and Ma teevra (sharp) then these Sandhiprakash ragas are sayankaleen ( to be sung in the evening.)
‘Madhyam’ can also alter the raga swaroop. Eg in raga Bhairav, Re Dha are komal and Ma is shudha. But, if the shudha Ma is replacedbyteevra Ma in the same composition, then it changes to raag Purvi, a sayankaleen raga. Or, if the shudha Ma is is replaced by teevra Ma in raga Bilawal, it becomes raga Yaman.
To sum up, the Madhyam swar gives us the guidelines to alter the raga samaya and raga swaroop. Barring a few exceptions, the Madhyam swar always manifests itself in its defined form in all ragas.