I have always been fascinated by artists who bounce between tonal extremes when performing, particularly the ones who serve their songs sad and their stagecraft salty.

Adele, for example, fills the space between each plushily upholstered soul-baring ballad by transforming into a saucy end-of-pier variety act, coo-cooing at the crowd and cursing like a squaddie. John Lennon gurned and clowned his way through the Beatles’ concerts, subverting the naked suicidal plea of ‘Help!’ in the process. John Martyn would belch and joust in mock-Cockney at the conclusion of a particularly sensitive piece. Jackie Leven punctuated songs of immense pain and sadness with eye-watering stories of defecating in alleyways and getting blootered with the Dalai Lama’s bodyguard.

A bipolar approach to performance can puncture reverence, acting as a knee-jerk spasm against stifling solemnity. It can also be deployed as a defence mechanism to protect overly exposed nerve endings. It is certainly one way to keep an audience on its mettle and in a state of pliable unease. Yet it can be hard to gauge how much of this approach is a conscious strategy, and how much the unfiltered leaking out of an artist’s innate nature.

Which brings us to Kathryn Joseph. A singularly serious artist, Joseph won the 2015 Scottish Album of the Year award with her debut album Bones You Have Thrown Me and Blood I’ve Spilled. She has delivered on that early promise. Last year’s For You Who are Wronged was widely acclaimed – and justly so. Her music is sparse and spooky. Her words have the plainly poetic cadences of a spell or a curse.

Yet in Edinburgh, she salted her sorrow with between-song tales of such intimate embarrassment one would hesitate to share them with a best friend, never mind a paying audience. In the scatological subcategory of performer’s pillow talk, Joseph is clearly an Olympian. Most of her stories are frankly unrepeatable, and served to yank the mood of the show between a hushed haunting and head-shaking hilarity.

With our nervous laughter still echoing around the Dissection Room (Summerhall is a former veterinary school), Joseph would place her hands on the keys to play another hypnotic pattern on the electric piano and sing another hypnotic song for the abused, the broken, the disposed of and dispossessed. As an audience, we were caught off-guard by the shift and left oddly vulnerable. It was a neat trick, if a trick is what it is, serving ultimately to accentuate the seasick rhythms of her songs and their agitated hearts.

Introducing herself as a ‘drunken old lady’, Joseph was here to sing her ‘creepy little sad songs’ about bones and blood and betrayal. In a sense, her set – part of Summerhall’s excellent Festival ’23 programme – was one long mood piece. She sat alone at the piano, from which she coaxed thick, chewy, undulating grooves. From time to time, she flicked a switch and a primitive, thudding pulse marked time.

Joseph has a pleasingly weird way with syntax – exhibited on the closing ‘What Is Keeping You Alive Makes Me Wants to Kill Them For’ – and an equally idiosyncratic way with rhythm. These circular incantations at times wandered into the blunted edges of trip hop: ‘Tell My Lover’ elicited faint echoes of Portishead. The cascading piano motif on ‘Of All the Broken’ – preceded by a tale about smashing her head open while playing on a children’s waterslide in France – brought to mind the squelchy, slippery time signatures of prog rock. There were stirrings of folk, soul and jazz, and moments which recalled the becalmed, almost-silent passages of Talk Talk’s albums Spirit of Eden and Laughing Stock.

Her voice curled at the edges as though singed, often sliding into an exaggerated miaowing vibrato, like an indie Eartha Kitt. Occasionally this elided into a wordless, primitive keen, suggesting a woodland creature in pain. ‘The Bird’, leavened with a music-box tinkle, felt as if it belonged to a lineage which includes both Billie Holiday and Beth Gibbons.

She played for a little over an hour, which was well judged. Joseph’s music isn’t exactly easy listening but there was much beauty to be found, and some solace, within her trauma-filled songs. ‘The Burning of Us All’ insisted that there was ‘no one coming’ to save the stricken protagonist, yet the closing verse held the promise of the cavalry arriving. ‘Mouths Full of Blood’ assured us ‘you will like this light’. For what is light without shade, and vice versa? Joseph asked the question, and she answered it too.