The music Industry is essentially split into various different sectors that all contribute to the overall industry. The most traditional thought would be that those who play music are in the music industry.Christopher Small (1998) argues that to be involved with music, you would be taking part in a musical performance, whether by performing, by listening, rehearsing or by providing material for performance (such as composing). As I am a music composer and producer, Small's point suggests that I am in the core of the musical production aspect of the industry. Although, many suggest that the industry is much more complicated than that. Hesmondhalgh (2002) and Wikstrom (2009) suggest that the music industry consists of music licensing and live music, as well as developing global personalities that may be exploited through various forms of media platforms. 

Sterne (2014) claims that "defining “music” as a commodity is extremely limited considering the range of commodities sold through, with, or around music, ranging from musical instruments, to hardware and software, to smartphones, to speakers and room architectures." (Sterne, J. 2014. pp-52)

There are lots of other factors to consider within the modern music industry besides the sale of recordings and performances, such as manufacturing, marketing, sales, and retail etc. These last sectors have heavily grown in the recent years, which have had a big impact on the wealth of the music industry, so who's to say that those involved within those sectors aren't actively involved in the music industry? 

Overall, those that would argue they work in the music industry may play more than one role. I claim I am a producer, however, I am also a skateboarder, rapper and a full-time student. Much like myself, there are other people out there that may class themselves as music industry workers who may also work within the social media promotion industry for example. To conclude I would argue that the music industry can not be defined as a single thing, rather an accumulation of the various sectors involved that share a similar interest. 

References:

Hesmondhalgh, D. (2002). The cultural industries. 1st ed. London: SAGE.

Small, C. (1998). 'Musicking: The Meanings of Performing and Listening.' Hanover: Wesleyan University Press, 1998.

Sterne, J. (2014). There Is No Music Industry. Media Industries. 1.1 (1), pp.50-55.

Wikström, P. (2009). The Music Industry: Music in the Cloud. 1st ed. Cambridge: Polity Press.