Solocontutti allows musicians to play together across the internet with minimal latency - low enough to play together in real time without delay. The app has been around for a while and has several thousand users. Recently it has been updated to allow it to be used with screen readers and has been thoroughly tested with Voiceover on Mac and Narrator on Windows. The current beta version with screen reader support is available on the site https://www.solocontutti.com/download_page.php (scroll down to accessible public beta) or direct download from https://www.solocontutti.com/download_page.php?file=1070 . The site contains detailed help and setup information. You can also contact us at email@example.com. A version supporting accessibility on iOS is expected after the summer.
There's also a Facebook community group starting up at https://www.facebook.com/groups/896843184243917