How to Stream Audio into a Call with Node-RED

This tutorial series aims to help developers get started with Nexmo's Voice API using Node-RED, a visual programming tool. The goal is to play an audio file to a caller during an inbound call or stream audio into a call for an outbound call. To achieve this, developers need to set up their environment by installing the necessary nodes and exposing their local server to the internet using tools like ngrok. They also need to create a Nexmo application and link their virtual number to it. The tutorial covers building a Nexmo Call Control Object (NCCO) to control the call flow and making an outbound call using the `createcall` node. Throughout the process, developers can follow along with example flows and use pre-built nodes to simplify the development experience.