Tala (or taal) means “rhythmic cycle”. In the Indian classical music, normally a rhythmic instrument like tabla or pakhawaj is used to accompany the music and keep a particular tala going on, while the singer or the player of a melodic instrument develops the melodic part of the musical piece.
Melody is not disconnected from the rhythm. In fact, in Indian classical music they are closely interconnected, and there are special points in the development of the music in which they meet in a very clear and pronounced way. These points are called sum (or sam). For this, musicians have to be well coordinated and each one has to be aware of what the other is doing. It means that a singer should have a good training in the rhythmic aspect; and the rhythmic accompanist should have a good understanding of the melodic aspect. In this way, together they can create a beautiful and unique musical presentation.
There are many different talas in Indian classical music, and each one has its own name, as well as a definite number of beats or time units (called matras) which are played or marked in a specific way. For example, Dadra is a tala which has 6 matras. Below you can hear examples of Dadra played at different speeds (laya):
Dadra – madhya laya (90bpm): ouvir-dm
Dadra – drut laya (180bpm): ouvir-dd
The following talas are commonly found in Prabhat Samgiita: Dadra (6 matras), Rupak (7), Kaharva (8), Bhajan theka (which is a variation of Kaharva and also has 8 matras), and Teen Taal (16 beats). Below you can see some examples of how they sound like:
Rupak – madhya laya (90bpm): ouvir-rm
Kaharva – drut laya (150bpm): ouvir-kd
Teen Taal – vilambit laya (30bpm): ouvir-tv
Teen Taal – drut laya (180bpm): ouvir-td
In the most basic and simple form of a tala (called theka), each beat is marked by a specific stroke (or combination of strokes) of the instrument. Each stroke is named after the sound which it produces (that is, the name is formed onomatopoeically). The name of a stroke is generically called bol (meaning “word”). Taking again the example of Dadra, its bols are: dha, dhin, na, dha, tun, na. Variations in the basic bols do exist. So, both Kaharva and Bhajan theka have 8 beats but the way they are played is so significantly different that they were given different names.
Each tala is also subdivided in a definite way. For example, Dadra is subdivided in two sections with 3 matras each: 3 + 3 = 6. Each section (vibhag) is characterized by a emphasized beat (tali) or by a non-emphasized beat (khali). In the case of Dadra, the first section starts with tali and the second one with khali.
In the following link you can see a document presenting the basic characteristics of selected talas: click here to open (with option to download). These are talas which we have found in Prabhat Samgiita or in other compositions we have studied.
You can refer to the following educative webpage for more details, didactic explanations and illustrations (including audios and videos) of the main concepts related to tala: http://raag-hindustani.com/Rhythm.html. In particular, it has nice audiovisual examples of how tala and the lyrics of a song are coordinated.