ghazal is a kind of poetic expression of a concept or theme. This is a type of ancient music & the roots of this are from Arabic poetry. In ghazals meaningful words and the pronunciation is very very important. Style of ghazal singing is different one and unique. Singing ghazal is difficult and to understand the complex lyrics of ghazal are more difficult. So there is a separate class of people (ghazal lovers and followers) in music industry.
Normally Harmonium, Tabla, Bulbul, violin, etc. type of traditional instruments are used in orchestra for ghazal. In ghazal shows preference is given to lyrics and presentation of singer singing it, so only supplementary instruments are used.
Nature of ghazal singing or orchestra for ghazal is soft. Even after that we find separate group of audience for this category of music.
