To switch ON/OFF your Music 1 or Music 3 speaker press and hold the power button located on the lower left hand side. A short press will, when powered on, show the current battery charge level via the volume indicator LED’s.
Music 5 and 7 don’t have a physical ON/OFF button. They will either be ON, in standby or in deep standby. Read more about standby modes here.
To power on a Music 5 or 7 in deep standby, simple feed it a signal (Wi-Fi, Bluetooth or cable), or bring your hand close to the top panel to trigger the proximity sensor.