Apart from its intrinsic interest, the relationship between music and verse is of particular concern because of the often-mooted possibility that music may have made a significant contribution to the developments that took place in Hijazi poetry during the first/seventh century. Discussions of the various categories of music are rather more instructive. Two main types are distinguished, hudā and ghinā, the latter further subdivided into naşb, sinād and hazaj. In relation to the poetic corpus, the term 'pre-Islamic' may in the present context be regarded not literally, as a confident statement of date, but rather as an indicator of social background and mode of composition. The balance between music and verse may also have been subtly affected by changes in the relationship between voice and accompanying instruments. The one obvious area where one might conceive of a stable, consciously maintained and readily quantifiable relationship between early Arabic music and verse is in fact in their rhythmic structure.