But don't let that be a turn-off: Arnalds' mostly instrumental songs, which fall somewhere between contemporary classical and experimental electronica, are gorgeously textured sketches with as much restrained hope as melancholia.

NPR: Olafur Arnalds: 'Vid Vorum Sma'

Inside, a belly dancer performed live, and a DJ spun '80s and contemporary music while Yelp's 2, 000 guests--mostly folks in their 20s and 30s who are fans of the site--danced and ate finger food prepared by San Francisco restaurants.

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