When you place a call on hold, a default system file will play music for the caller to indicate they are still connected to the call and waiting for you to return. If you wish to change the default audio that plays for callers who are on hold: Navigate to Settings → Account Settings, then click or scroll to the section labeled Hold Music. Click the cloud icon in the Custom Hold Music field. In the pop-up that appears, click the System Recordings tab to view all available presets. If you have a different file you'd rather use, follow the instructions here for managing your own audio files in the account.