Automatic audio playback of displayed textual content

An audio playback system that provides intuitive audio playback of textual content responsive to user input actions, such as scrolling portions of textual content on a display. Playback of audio (e.g., text-to-speech audio) that includes textual content can begin based on a portion of textual content being positioned by a user input at a certain position on a device display. As one example, a user can simply scroll through a webpage or other content item to cause a text-to-speech system to perform audio playback of textual content displayed in one or more playback section(s) of the device's viewport (e.g., rather than requiring the user to perform additional tapping or gesturing to specifically select a certain portion of textual content).