Have you seen those multilayered, almost Brady Bunch–looking, videos of people singing and accompanying themselves? That’s from an app called Acapella, and its parent company just announced a $1 million round of seed funding today. And if you haven’t seen one yet, get ready for a songbook. Launched just six weeks ago, the app has been an instant hit with young people. It allows you to take several videos of yourself, stacking the first videos over the next so you can sing over your own backing vocals, until you become an a cappella troupe of one.