The Afghan concept of melodic mode (rag) is very close to that of North Indian classical music. This is not surprising given the historical links between the musics of Afghanistan and North India, reinforced in the 19th century by the migration of musicians from what was then British India to Kabul as court musicians, and more recently the training that a few musicians from Kabul have received in Pakistan or India. As discussed in Chapter 2, Afghan music divides the octave into 12 semitones (nim pardeh) and names them accordingly Sa Ra Re Ga Ge Ma Me Pe Da De Na Ni Sa1. In this gamut of notes the tonic Sa and the 5th Pe remain stable, while the 2nd, 3rd, 6th and 7th can take either flattened or sharpened forms. Bilawal is just one of 32 scale types that can be systematically derived from the basic notes placed in different permutations and combinations.
But a rag is more than just a scale. It implies certain melodic combinations of notes that characterise the mode. Very often the ascending scale (arui, raft) differs in detail from the descending scale (amrui, amad). For example, in Pilu the arui is Sa Ga Ma Pe Ni Sa1, while the amrui is Sa1Na De Pe Ma Ga Re Sa. In Des the arui is Sa Re Ma Pe Ni Sa1and the amrui Sa1Na De Pe Ma Ge Re Sa. In Asa the arui is Sa Re Ma Pe De Sa1and the amrui is Sa1Ni De Pe Ma Ga Re Sa. In all three cases the arui is a 5 note scale, and the amrui a 7 note scale. Within the notes of the scale certain combinations of notes are to be avoided, others are to be emphasised. In addition, in most rags there is a single defining phrase that immediately reveals the identity of the rag. In Indian music this phrase is called the pakar. A further complication is that most modes permit the occasional use of notes that are not part of the "essential" scale. In Bairami all of the notes not part of the Bairami scale can be used in their proper place in carefully crafted phrases. Pilu also has much flexibility in this respect.
When playing a piece of instrumental music on the rubab it is customary to begin with a slow introduction in free rhythm that reveals the melodic characteristics of the mode to be played. Such an introduction is called a shakl, meaning 'face' or 'features'. It corresponds approximately to the alap of North Indian music, or the taqsim of Middle Eastern music. The introduction in free rhythm is a widespread practice in those parts of the world. There is a strong element of extemporization in the performance of a shakl, though the rules of the rag must be strictly adhered to. For each of the six compositions presented in Chapter 5 I give a number of possible shakl phrases but these are in no sense definitive. Developing the ability to create a shakl in performance is an important aspect of the rubab player's art.