Grid for iPad from SmartBox is a communication app for iPad. You can access it via touch or switch, and from iOS 13 onwards, mouse or pointing device. It offers a wide range of grid sets for communication, with symbols or text, with content for all ages and abilities.
Grid for iPad can be bought outright or with a monthly subscription and a 30 day trial is offered.
Step 1: Within the Grid app, go to 'Settings', choose 'Speech', then 'Voices'.
Step 2: Scroll down to find the voice you want in the Downloadable voices section, select the voice you want and choose 'Download'.
After the voice has downloaded you can adjust the pitch and speed by using the 'Configure' button.