No, I am not talking about inter-planetary distances here🙂 Graha bheda is a term that means shift of the base note in Indian music.
Unlike some other musical systems where compositions are tied to specific octaves (or base notes, or tonics), Indian classical music does not have a fixed reference for performing. The performer chooses his or her own pitch and sings a composition. This becomes the AdhAra shaDja – or the base note for the performance.
Performers sometimes execute a graha-bedha during their singing; This means that they switch the base note for short intervals, and create a different rAga, and a different mood). Graha means base note, and bheda means to differ. So Grahabheda implies a shift in the tonic.
This requires a degree of finesse to do an effective, and elegant graha bheda. It is a challenge to a vocalist, comparatively trivial to instrumentalists.
Here is an example that I came across today🙂 Sanjeev Abhyankar switching to guNakali ( I suppose it is :)) when he is singing rAga Bhinna Shadja. I am posting the links from YouTube (Courtesy: rmoudgalya)
(The grahabhEda happens in the 2nd clip, and Sanjeev also illustrates where he changes the shaDja)