The Nexmo Voice API allows for recording inbound and outbound telephone calls, but manually classifying these recordings based on their content can be time-consuming. To automate this process, a tutorial is provided on using Natural Language Processing via Google Cloud Services to classify the content of each recording. The tutorial requires a Vonage API account, a virtual phone number, and enables two Google Cloud Services APIs: Cloud Speech-to-Text and Cloud Natural Language. It uses Flask to serve an NCCO file, instructing Nexmo to record calls, and Huey for background tasks to download the recordings, transcribe them into text, and classify their content using the Google Cloud services. The tutorial also includes code examples and instructions on how to set up the necessary environment and credentials.