@AiTitus :)
As of now, you cannot place a custom background music or any background music on call transfer until the specialist or the agent answers the call unless you are using Twilio. Using Twilio hacks, you can do it. Regarding the topic which you are asking for, it's called OnHold specialist transfer. I know it's a hard one to follow and half baked. But we can improve it based on your feedback
https://docs.vapi.ai/calls/call-handling-with-vapi-and-twilio