For each phone number, you can set custom music or a message that plays when the customer is put on hold.
To add a custom hold greeting:
Go to Admin Settings > Phone Numbers. You can see the list of available numbers in your account. If you do not have any number, you can purchase a new number using the Buy New Number option.
Hover over the number for which you want to set a custom hold music and click on the edit icon. You will see the Number Properties tab.
From the Custom Hold Message option, select the tune or message you want to play as the hold message to the customers.
If you do not have any message, click on the New Message option to create a new message.
Click Save Changes.