Tonight I’m at the Purcell Room in London to see Tift Merritt and Simone Dinnerstein playing their 2013 album “Night” (plus some additional tracks that we were lucky enough to hear). I don’t know that there’s a duff arts venue in the whole of the Southbank Centre. The BFI quickly became the only place I ever want to watch films, the galleries and theatres are tremendous, and I’ve seen some wonderful and unique concerts here over the years. The location as a whole warms my heart, especially in winter when they put the blue lights out in the trees along the river bank.

So here I am, happily and comfily ensconced in a leather-bound seat in the centre of the auditorium doing the crossword before they start while Tift Merritt tunes one of her guitars. I have another stab at 6 down, look up having failed again, and she’s gone. Frustrated crosswording continues until the house lights drop and Tift and Simone quietly emerge from a small gap in the heavy drapery around the back of the stage.

There’s a Steinway & Sons grand piano, two guitars, microphones, a piano stool, a small clutch of monitors and two chairs, one draped with Tift’s shawl. While Simone welcomes us gently with “In the Evening”, Tift sits to the side – a mutually respectful standing-away that they perform as the songs ask.

The prelude over, the two combine to drop our jaws with the one-two of “Only in Songs” and “Night and Dreams”. It’s a lacerating opening and in many ways sets the tone for everything that is to come.

It took me a little while to warm to the record but then that’s often the case when you’re pushing some of your own boundaries. There are songs on it that, in the plainer setting of CD or earphone commuter listening, I like, but not strongly. Here, tonight, in this place, every one of them is transformed, super-powered, glowing with life.

“Wayfaring Stranger” has long been a standard I tried to avoid; even on the record I find Tift’s version compelling but here it is irresistible. The Elizabethan/folk traditional “I will give my love an apple” is the kind of song I traditionally sidestep like BBC period drama but the recorded version was beginning to persuade me otherwise. Tonight I can scarcely cope with this heart-crushing track, and I am overcome by the picked piano-strings and the final line: “and he may unlock it, without any key”. It feels like tonight, I finally get it. Watching Simone Dinnerstein teasing those terribly beautiful notes out of the grand is a melancholy highlight.

The transition from that song into “Colours” also revealed itself in majesty. I’m listening to the album now on my train home and my god, how different it sounds to me now, better-understood, revealed. What moments these are.

Dinnerstein is mesmeric – augmenting, revising, overlaying, exposing the bones of “Suzanne” in the Cohen Variations and, on an instrumental that I hope she will forgive me for forgetting the name of, I am pulled forward in my seat to stare open-mouthed, dumb, at the relentless speed of her fingers, tumblingly hypnotic, and the fluidity of her playing.

There are several lovely moments of interplay between Simone and Tift and the audience who for the most part are so busy politely concentrating on the performance that they can’t readjust to the moments of levity, laughter and friendship between songs. Tift wonders at one point how her jokes are falling flat; for the same reason that there is a moment of amazing silence after the opening triptych, with us frozen in our seats so captivated that we forget to even think about clapping, then, when we do, for a moment we feel it might have been impolite to break the mood that had been so carefully, passionately created. She gets us though, joking about the irony of endlessly playing the song “Spring” through a doggedly persistent Winter that would not quit, and that there is “no-one else in the world who appreciates that [situation] more than you guys” this year.

If I have to pick a favourite moment it’s probably their reading of the Nina Simone arrangement of the Billie Holliday song “Don’t Explain”. This is one of those occasions where, despite having been a fan of someone for a long time, you feel like you never really heard their voice before – the tumult of emotions is perfectly conveyed with an expressiveness that is raw and captivating. A magnetic delivery of a tremendous song in a thrilling performance.