There is a misconception that this Khyaal gayaki is very old and has ancient roots. The Dhrupad gayaki definitely has ancient roots tracing back to the vedic age in its development but not the “Modern” Khyaal gayaki. The Khyaal gayaki that we hear now in the form of Bada Khyaal , chota khyaal , tappa , thumri etc is quite recent, not more that 100 years old , even less.
In fact , the Khyaal gayaki is the “Pop” music of the traditional classical music,which was Dhrupad gayaki. Khyaal gayaki is now accepted as a Classical Music of India !
The times of Akbar-Tansen through the 18th century Dhrupad gayaki was in vogue and was the only form of music. The other gayaki was purely folk singing !
Khyaal gayaki came in through Persia to the Indian subcontinent when verses of poets were vocalized with the aid of Dhrupad musical framework.
The raags in Dhrupad framework were not defined by aroha-avaroh- bandishes etc but by Moorchanaa of Shuddha swars (modern day Bilawal scale ) classifying into 6 basic “types” of main (male)raags. ( Bhairav , Malkauns , Deepak , Shree , Megh and Hindol). There were Raaginis (5 from each) derived from these basic raags and also sons (putra) and “daughter in laws” giving a total of 84 ragas.
These raags were simply defined by the Gandhar , Madhyam and Pancham moorchanaas of basic shuddha scale.
The Khyaal gayaki that emerged with the arrival of Persians weaving bandishes of verses for various raags made it more appealing. Some of the raags faded and some became very popular in performances. Nineteenth century saw the real popularization of this style of Khyaal gayaki that we currently label as Indian Classical Music or Hindustani Classical Music. This was the period when lyrics were put in as bandishes of various raags. Most of them either in Braj , hindi dialects , urdu , Rajasthani , Punjabi or some North Indian dialect.
The Gharana system developed with the popularization of this type of singing using the base of Dhrupad with lyrics signifying a mood and thought ( khyaal).
As one can see, most of these Gharanas are based in Northern India with the patronage by princely states .. Gwalior , Agra , Jaipur , Patiyala , Mewati , Delhi , Kirana, Rampur-Sahaswan , Benaras etc.
With the base training of Dhrupad style , most of these gharanas adopted the Khyaal gayaki for performances. They also had their special bandishes for training the disciples , that unfolded the raag in a particular fashion characteristic of the gharana. Eventually , the Dhrupad gayaki only remained limited to certain gharanas e.g Dagar , Betia and Darbhanga.
The true popularity of the current Indian Classical Music style gathered momentum only in late 19th century and early 20th century (1890-1940). The Thaat system was invented by Late Pt Vishnu Narayan Bhatkhande. This made the classification of Raags and scholastic training in “Indian Classical music” relatively easy. With the popularity of this style of music , various artists grew interest in this form and style. With the advent of notation system by Pt Vishnu Digambar Paluskar , it was easy to transcribe the knowledge gained through traditional aural tradition on to paper. Pt V D Paluskar also founded the Gandharva Mahavidyala for training students of the modern form of Indian Classical Music. His son Pt D V Paluskar and other disciples like B R Deodhar , Onkarnath Thakur , Naraynrao Vyas , Vinayakrao Patwardhan continued his pioneering work of popularizing and promoting the Indian Classical Music in the form we hear it today.
The Bada khyaal-chotaa khyaal bandishes , tappa , thumri gained popularity in masses. There was also an inclusion of folk music though in meager amount. Pt Kumar Gandharva created raags based on various folk tunes that he heard in remote villages and places across India.
Various other artists did a similar creative work e.g Pt Ravi Shankar , Ut Vilayat Khan , Ut Bade Gulam Ali Khan (who popularized surmandal for vocalists). New raags were created by maestros. The true popularization and acceptance of the current style of Indian Classical Music by public , intellectuals and patrons happened in mid 20th century around 1940-1960. Eventually the classical musicians made their way to film music (Naushad , Mohd Rafi and many ) . Abhang, Natya-geet, gazal , thumris were included in the “Classical Concerts” due to their popularity with masses, as light variants to entertain the the growing base of patrons.
Thus, the Classical Music that we listen to and admire today in its current form is not very old. In-fact , it has evolved as a “popular form” (pop music ! ) derived out of Dhrupad style, that has ancient roots.
So the next time someone says that Indian Classical Music is ancient, do not believe it .. the bandishes , the style and compositions are not more than 100-150 years old !