With a line-up of all sorts of famous artists you've already heard a lot about taking to the stage across the city, the sense that little St Luke's might have been overshadowed in third place on the BBC 6 Music Festival bill was emphasised by the thin Saturday evening crowd in the hall at half past six, twenty minutes after one of the finest Scottish groups on this extensive roster were meant to start their set. Yet within minutes of DJ veteran Liz Kershaw taking the mic, rolling her eyes at the relative scarcity of women artists visible on the bill, and promising to change that to an extent here, the place was full.

Even the gorgeous weather couldn't keep the people outside, with Rachel Aggs – lead singer with Sacred Paws, that aforementioned great Anglo-Scots group – observing excitedly that the East End had felt like California throughout the day. There couldn't have been any more appropriate conditions, then, to experience the rich and joyous sound that Sacred Paws make, a cheerful and enthusiastically dancefloor-enabled fusion of afrobeat and post-punk which skirts the edges of perfect pop music as well.

For Haley Bonar, the weather was also on her mind. 'I saw a lot a Scottish people tannin' today, I've never seen that before,' drawled the South Dakota-raised singer, although her music isn't as breezily summer-enabled as the band which preceded her set. 'Your Mom is Right' rode on meaty guitar lines and the lively, fighty 'No Sensitive Man' blew through the venue, even as the more parched slide guitar country tracks demonstrated the tender power of Bonar's voice.

'You guys are an audience ready for radio… I don't know what that means,' waffled New York's The Lemon Twigs, possibly one of the most anticipated and idiosyncratic bands of the weekend. In brothers Brian and Michael D'Addario's music there's both a sense of raucous indie-pop fun and an epic, baroque emotional sweep reminiscent of Magnetic Fields, Hidden Cameras and Flaming Lips, by turns. From the piano groove of 'These Words' to the precise emotional punch of 'I Wanna Prove to You' and 'As Long As We're Together', their tweeness is infectious and easy to fall for.

Seattle's Car Seat Headrest, meanwhile, closed the show doing a fair impression of The Strokes if the latter band actually had been the future of rock and not a flimsy hype construct. Wildly prolific (last year's Teens of Denial was their tenth album in six years), they're also a vigorous and masterful live proposition, and a fine conclusion to an evening of excellent new music. It's more than likely that at least a couple of the names here will also be famous artists everyone has heard about before long.

BBC 6 Music Festival 2017 can be watched on BBC iPlayer.