In a marquee in the courtyard of the Three Sisters pub, the tent flaps aren't fully secured, inviting steady background babel to sneak through the façade: loud, lounging day drinkers; children and the balloons they can't keep un-popped; big-screen football racket and its fans. At the head of this sweltering tent, Sophie Grant is at the keyboard serenading a contiguous audience of fans, passersby, drag-alongs and reviewers with a series of jazzy, soul-esque renditions of well-known songs. The theme for the day is 'travel'; the song choices range from Simon & Garfunkel's 'America', through Carole King's 'So Far Away', arriving at destination Marvin Gaye's 'Hitch Hike'.

Her show, Mixtape, is inoffensive to the highest degree and perfectly placed to highlight the two-faced nature of the selection music fans can expect during the Fringe. In the next week alone, music fans – the ones who follow the scene, still pay for music, and have a distinct taste in what is good versus what, in their humble opinion, is not – can take their pick from Withered Hand, King Creosote and Mogwai - three behemoths of the Scottish scene. Not to mention the legacy that has passed before them: Kathryn Joseph, WHITE, Anohni, Billy Bragg, Mairearad & Anna, Young Fathers and Sigur Rós over the past two weeks.

Where, then, does this leave shows like Mixtape, whose makeshift aesthetic and tenuous themes languish in the music section of the Fringe brochure, running on for their full three weeks before disappearing, at least from Edinburgh, leaving nothing but a discarded flyer in memoriam? Shows like Starman and My Leonard Cohen and any performer who takes a concept, whips it into a Fringe show and treks to Edinburgh to find its indeterminate audience.

Trying to compare these shows with the aforementioned gigs of the Fringe is redundant; those audiences are not the same, nor do they aspire to be similar. The gigs sell out, the full-Fringe runs do not. The gigs have the fanbase; the runs have the drop-ins and the curious. This shouldn't diminish the appeal of the longer runs. There is a time and a place for these kinds of shows; that time and place is August in Edinburgh.

Mixtape is harmless: you'll know the songs, Grant can sing well, and it's a perfectly pleasing respite from the Cowgate crowds. Is it going to rock the music industry? No, but it's not trying to. But its parallels run deep with an Edinburgh that's trying to revitalise its music scene. We once had Flux Festival, then T on the Fringe, then The Edge Festival to see us through a comedy- and theatre-centric August.

While stalwart shows at the Queen's Hall and Summerhall's new Nothing Ever Happens Here series, are a valiant effort to give Fringe goers a one-off sonic spectacular, they're not mainstay Fringe shows - these would be happening whether the Fringe was around or not. We cannot hold shows like Mixtape to the same values as we do big-name musical acts - these are entertainment shows, while the curated concerts are more aligned with the cultural experience we expect from the Fringe.

Laughing Horse @The Free Sisters, until 28 Aug, 12.45pm, free.