You've done karaoke in dive bars, piano lounges, even those Korean-style karaoke spots with private rooms so no else has to hear you butcher "Like a Prayer." But have you ever belted out Britney while sipping a top-shelf cocktail and checking out bird's-eye views of the Mall? Now you can: The W Hotel is kicking off karaoke in its all-weather rooftop lounge this week. Fresh 94.7 DJ Tommy McFly is the host of the party, where the musical focus is Top 40 tunes. Get up your courage with $10 cocktails, and who knows, the top vocalists will take home prizes. And while getting up to the W's rooftop can sometimes be a gamut of velvet ropes and clipboards, this night doesn't require reservations. Just show up any time after 6:30 p.m. to warm up; singing runs from 7 to 10.