Suggest the best text to speech converter with natural sounding voices available.
I develop online courses on various technical topics. I want to add soft and pleasant human voices to the course which can enable easy understanding of the course content by its users. Hiring a professional language expert incurs a high cost and also restricts me from making any updates to my courses. Can anyone kindly suggest me good text-to-speech conversion software which has natural sounding voices so that it can help me get my job easily done?