The tempo of rhythm is never changing in Alap and all the cycles of Tala remains a constant in Alap and this provides a firm foundation to Alap. Within the cycles of this constant, various permutation and combination of notes are created. They are changed every time and a new thought is created every time. Thus a new Alap is in turn generated. They constitute the variables in this process. Placing these numerous variables in one process with slow sequential progress of Bhadat is what constitutes Alap singing. In short it is a variable of music thought superimposed on a constant mode of rhythmic beats.
A Sthayee of a bandish is a compact Raaga representation itself and it establishes framework of the entire Raaga. Antara is almost like a Sthayee, displaying the same characteristics, except in the higher octave. Sthayee and Antara together complete the picture of the given Raaga in all octaves. This is accomplished primarily through Alap. With Alap as a firm foundation, a complete structure of Raaga can be created during Vistar.
Role of Mukhada in Alap Presentation
There is another detail that takes place during Alap presentation. While singing in any genre of Hindustani music, especially a Khayal, the very first line of the Sthayee is considered as the main chorus line, called Mukhada. Mukhada plays an important role during a Raaga development. The role of Mukhada is to signify the end of each Alap. It differentiates between two adjoining Alap. During Alap singing, a singer approaches the first beta of the Tala called Sum and of the next cycle with a Mukhada, thus, marking an end to the previous Alap. Prior to ending with a Mukhada, returning to the starting point is also practiced. Such a practice makes every Alap seem like a complete cycle. This cycle is in turn placed in another circle, that of Tala with Mukhada as its climatic point. Thus it can be said that one cycle of notes in some combination being placed in another cycle of rhythm with Mukhada at its end is what constitutes Alap. After rendering Sthayee and Antara with all possible variation of musical notes a singer can create Alap presentation is regarded as complete.
In short as Hindustani music unfolds the process of improvisation or Vistar is carried out in a very systematic order. With Sthayee and Antara as two main parts of Khayal, the lower and upper halves of the main melody go together as two aspects of an integral whole. Therefore the uniqueness of Vistar stands out even prominently during Alap presentation.