It's Monday night in Lazimpat, traffic slows, shop windows darken. Live music pulls you down an alley to a lit doorway. Up the narrow stairs, the music swells, and then you are inside. People are seated at low wooden tables with beers. Fumes from the kitchen below mix with cigarette smoke.

Steaming plates of alu dum or momos are ferried to customers through the squeeze of people. The wall space is crammed with fading black and white photographs of Billie Holiday, Louis Armstrong, Ella Fitzgerald, Charlie Parker, and Duke Ellington. An enormous poster of Miles Davis's face, eyes closed in ecstasy, is plastered behind the drummer. This is Jazz Upstairs, and Ramshackle, the blues band which plays every Monday, has just launched into a mournful, swinging rendition of Jerry Reed's Bright Lights, Big City.

Marcus Dengate plays moody slap-bass solos, referring to his bass as his "wife". In the middle of a song he'll sometimes call out for 'fuel' (a refill of whisky). He is a familiar face on the Kathmandu music circuit. Rishav Acharya is a young drummer born and raised in Kathmandu, and plays with four bands including Silver Wind Quartet, the jazz band that performs at Jazz Upstairs every Wednesday and Saturday. Acharya is a versatile player, adaptable to any style and always dynamic.

The singer and guitarist Desmond is rail thin. He brings his face close to the microphone with a kind of wonder you'd expect from a man much younger. Long, wavy white hair tucked under a straw fedora, his mouth invisible beneath his white moustache, Desmond sings every song with disarming innocence. His voice is made for the blues: half-growl, half-sweetness�always on the verge of breaking�a twangy ribbon of sound. He has the swagger of a man who has lived through everything. His guitar solos are moving and powerful and yet there is always a lightness to Desmond's playing that infuses even the blackest tune with levity�a sudden guitar riff that sounds insubstantial as The Beach Boys.

This balance of deadly seriousness and playfulness is at the centre of Desmond's understanding of the blues. "Inside it," he says softly, "there's this wellspring of joy. People might think the blues are gloomy, but you don't listen to the blues to sit and weep into your beer." Over the course of the night, Ramshackle performs Freddie King's Hide Away, Buddy Guys's Nineteen Years Old, Neil Young's Hey Hey My My, Hendrix's Little Wing, and many others.

Ramshackle's unpolished style infuses old hits with rawness. One song Ramshackle performs is haunting�it has a bare-boned, gentle melody that repeats, gathering emotional resonance with each repetition. Most of the song's momentum is provided by the lyrics. "Sirens wail / words all fail / to describe the thunder / of your blood in my head." Afterwards, Desmond confesses the song is his own composition, entitled Gone Girl.

Jazz Upstairs may be demolished soon, its days are numbered. Desmond says before bowing out: "Let's hope we'll be back here for another Monday."