Prototype. Point your camera at the QR code next to any level in the book: its grooves are added to your library and stay on this device. Turn on Play with the band to add bass, keys, guitar and strings that follow the groove. The codes contain the grooves themselves, so the app is empty until you scan the book.

Sounds: Virtuosity Drums, Black And Blue Basses, Growlybass, VSCO 2 CE and FreePats FSBS guitars (CC0); Salamander Grand Piano by Alexander Holm (CC BY 3.0); Wurlitzer EP200 by Greg Sullivan (CC BY 3.0); FluidR3 organ and clavinet (MIT).