Persian music works according to a unique system. There are two essential terms ,"Dastgâh" and "Radif", which you need to understand Persian music. The Persian music that we are going to talk about can be called Persian art music, Persian classicl music, Persian traditional music or Persian court music, but I think the most appropriate combination is Persian Dastgah music. Dastgah in Persian in general means "System", but you can not translate it to system, when you are talking about Persian music, Dastgah is a musical system, but a unique one, that exists in Persian music and I think in Azerbaijani classical music. You can consider the term Dastgah from two points of view, first a Dastgah as a musical system and second a Dastgah as a set of melodies, which have been ordered according a special rule. Radif is a collection of one version of any Dastgah or the repertory of Persian art music.