Gunn's Historical Enquiry Respecting the Performance on the Harp in the Highlands of Scotland was his most purely historical, only non-pedagogical, only commissioned, and most frequently cited publication. It was an entirely antiquarian concern. The historical research is wide-ranging, the range of references polyglot. Harp and the Dissertation in Violoncello 1 are connected, as Gunn says in a postscript to Harp where he explains that in the Dissertation there had been ‘a chasm in the history of the Harp … which I was unable, from any authentic documents, to fill up’. Here he may be recalling Burney, who wrote his history of music to fill ‘a chasm in English literature’.

Gunn wrote Harp at the request of Highland Society of Scotland. This had been founded in 1784 as the Highland Society of Edinburgh and officially renamed the Highland Society of Scotland in 1808, although known by that title before that date. (It is known today as the Royal Highland and Agricultural Society of Scotland.) There were two such societies at this time, the Scottish one and the Highland Society of London, with somewhat different priorities. Even in its early years the Scottish society's interests were more agricultural and historical than musical. Its aims were:

Cultural questions came third. The Highland Society of London was older, founded in 1778, and put cultural questions first:

In the London list only the eighth and last items concern agricultural improvement. Admittedly, the Edinburgh society's annual piping competition always took place in Scotland, but it had been initiated by the London society in 1781, which retained control over prize money and rules.