Khayal was popularized by Niyamat Khan (a.k.a. Sadarang) and his nephew Firoz Khan (a.k.a. Adarang), both musicians in the court of Muhammad Shah Rangeela. Khyal or Khayal, is the modern genre of classical singing in North India. Its name comes from an Arabic word meaning "imagination". It appeared more recently than dhrupad, is a more free and flexible form, and it provides greater scope for improvisation. Like all Indian classical music, khyal is modal, with a single melodic line and no harmonic parts. The modes are called raga, and each raga is a complicated framework of melodic rules.
Khyal bases itself on a repertoire of short songs (two to eight lines); a khyal song is called a bandish. Every singer generally renders the same bandish differently, with only the text and the raga remaining the same. Khyal bandishes are typically composed in a variant of Urdu/Hindi, and sometimes in Marathi or Punjabi, and these compositions cover diverse topics, such as romantic or divine love, praise of kings or gods, the seasons, dawn and dusk, and the pranks of Krishna, and they can have symbolism and imagery
Dhrupad, is a more free and flexible form, and it provides greater scope for improvisation. Like all Indian classical music khyal is modal, with a single melodic line and no harmonic parts. The modes are called raga, and each raga is a complicated framework of melodic rules.
A typical khyal performance uses two songs — the bada khyal or great khyal, in slow tempo (vilambit laya), comprises most of the performance, while the chhota khyal (small khyal), in fast tempo (drut laya), is used as a finale and is usually in the same raga but a different taal. The songs are sometimes preceded by improvised alap to sketch the basic raga structure without drum accompaniment; alap is given much less room in khyal than in dhrupad.
As the songs are short, and performances long (half an hour or more), the lyrics lose some of their importance. Improvisation is added to the songs in a number of ways: for example improvising new melodies to the words, using the syllables of the songs to improvise material (bol-baant, bol-taans), singing the names of the scale degrees — sa, re, ga, ma, pa, dha and ni (sargam) — or simply interspersing phrases sung on vowels, usually the vowel A, akaar taans. Taans are one of the major distinguishing features of the khyal. Now and then, the singer returns to the song, especially its first line, as a point of reference. Besides the vilambit (slow) and drut (fast) tempos, a performance may include ati-vilambit (ultra-slow), madhya (medium speed) and ati-drut (super-fast) tempos. Song forms such as taranas, thumris or tappas are sometimes used to round off a khyal performance.
The compositions of Sadarang and Adarang employ the theme of Urdu love-poetry. The khyal of this period also acquired the dignity of Dhrupad and the manner of the veena in its glide or meend, plus a number of musical alankars that were introduced into the body of the composition. The gharana system arose out of stylistic rendering of the khyal by various subsequent generations of musicians. The gharanas have distinct styles of presenting the khyal — how much to emphasize and how to enunciate the words of the composition, when to sing the sthayi and antara, whether to sing an unmetered alap in the beginning, whether to do bol-alap or aakar-alap, what kinds of improvisations to use, how much importance to give to the rhythmic aspect, and so on.