Both essays and reports are documents written with a purpose - to communicate a viewpoint, supported by analysis. The analysis includes discussion of evidence.
Essays are usually thematic, with an organic narrative structure. They have clear introductory and concluding paragraphs. But in between, they may describe points of view, compare and contrast different views, meander into examples, then return to the main theme.
Reports usually have clearly marked sections, perhaps with numbered headings. The headings may be hierarchical. A report will often start with a title page, and offer an executive summary. It will waste little time before marching into the introduction, background facts and methods (methods used to research or analyse the issues), then discussion and conclusion. Different disciplines (such as science and business) will have their own conventional formats.
You'll find a LibGuide on referencing in music and music business at http://libguides.bhtafe.edu.au/music-referencing