Twilio now supports Amazon Polly Neural Text-to-Speech (TTS) Voices allowing you to use higher quality voices with TwiML <Say> in your voice applications. The ground-breaking improvements in speech quality come through a new machine learning approach which converts text into lifelike speech. Amazon Polly Neural voices are currently available in two speaking style voices - Newscaster and Conversational and across four languages - English (British), English (US), Portuguese (European), and Spanish (US).
Try these voices in your IVR applications by selecting them in the TTS console or by setting them in your TwiML <Say> attributes. For more information on the voices and on pricing, please visit Twilio Text-to-Speech docs and Amazon Polly docs.