Los Angeles, July 30 : An impromptu live performance from 20-year-old Grammy-winning singer Billie Eilish drew huge crowds at Amoeba Hollywood that too at a few hours notice, reports Variety. This weekend, her second studio record, 'Happier Than Ever', celebrates its one-year anniversary, and on Friday afternoon (Pacific Standard Time), she took to her iconic hometown record store to perform an acoustic set of selections from the record. According to Variety, fans crowded every nook and cranny of Amoeba's new Hollywood location to see the singer play a four-song set. Finneas, the singer's brother, producing partner and tourmate, joined her onstage with an acoustic guitar and supporting vocals. Variety adds that after opening with 'Billie Bossa Nova' and performing 'TV' off her recent 'Guitar Songs' EP, Eilish left it up to the crowd to decide the next song, which resulted in an impassioned shouting match that settled on 'Getting Older'. Finally, the dynamic energy of the record's title track translated incredibly well into acoustic form, spurring an inspired crowd sing along that Eilish effortlessly led as the set's closing number. At the end of the performance, the singer thanked the crowd and left fans with the most Billie Eilish mic drop possible: "And happy 'Happier Than Ever' anniversary, b****." Between songs, Eilish thanked fans for coming out on very short notice to see her and Finneas play, noting that the one-year anniversary of "Happier Than Ever" also falls on her brother's 25th birthday. Reflecting on the record's anniversary, Eilish, quoted by Variety, told the crowd: "You guys are just the best. It's been the most amazing year, and you've been so sweet and respectful about this album, and I just love you!" The siblings are in the middle of a month-long break from their 'Happier Than Ever' world tour in support of the record, which kicked off in early February at New Orleans' Smoothie King Center and is slated to conclude at the end of September in Perth, Australia. /IANS