When playing Harp, you may not wish to be interrupted by a phone call, alarm, or SMS. However, there is no way that Harp (or any iPhone application) can avoid these interruptions for you— you must do it yourself by deliberately silencing your iPhone or iPod. Here are the steps that Apple recommends:

1. In the Settings application, ensure that the iPhone has Airplane Mode turned on.
2. In the Calendar application, ensure that there are no event alarms enabled during the planned performance period.
3. In the Clock application, ensure that there are no clock alarms enabled during the planned performance period.
4. Do not move the Ringer/Silent switch during performance. When changing Ringer/Silent mode, an iPhone may vibrate, depending on user settings.
5. Lastly, do not plug the iPhone into a power source during performance. When an iPhone gets plugged into power, it beeps twice or vibrates, according to user settings.
6. Update: iOS 4.0 introduces “local notifications” which are alarms that apps can set themselves. So make sure none of the apps you use have any local notifications set to trigger during the planned performance period..