Arabhi or Aarabhi (pronounced ārabhi) is a ragam (musical scale) in Carnatic music (South Indian classical music). It is a Janya raga (derived scale), whose Melakarta raga (parent scale, also known as janaka) is Shankarabharanam, 29th in the 72 Melakarta raga system.
Arabhi is a raga that dates back to 7 AD. Originally, it was called as pazhanthakkam in Ancient Tamil music. Then it was sung in a mixed variation of Devagandhari and Arabhi that is in use currently. These two ragas are clearly distinguishable in current form.
Its ārohaṇa-avarohaṇa structure (ascending and descending scale) is as follows (see swaras in Carnatic music for details on below notation and terms):
Arabhi raga is an Owdava-sampoorna raga meaning, 5 swaras occur in the arohana (so it is called Owdava) and in avarohana all swaras occur (so sampoorna).
It is a raga without much gamakas and frequency variations, relying instead on flat notes. The important point is the swara "ga" always comes very close to "ma" so when we sing the phrase "ma ga ri it sounds like "ma ma ri". Likewise the swara "ni" always comes very close to the swara "sa" hence when we sing the phrase "sa ni da" it sounds like "sa sa da".
The closest raga to this one is Devangandhari. There are few aspects which make Arabhi different (though both share the same ascending and descending scale, in terms of basic notation).
Arabhi raga is a very energetic and it lends itself to creativity in brigas (fast paced swara usages) more than gamakas.
The 3rd of Pancharatna Kritis (five gems of compositions), Sadhinchanae(also known as "Samayaniki Tagu Mataladene") by Saint Thyagaraja is a famous composition set in Arabhi raga. Here we can note that Thyagaraja uses phrases like "sa sa da" in the charanam although there are phrases like "sa ni da" also.