"He's doing well, he's resting up," says his friend and music producer, Jimmy Napes.
"He's got an app that speaks for him and it's like Stephen Hawking, where you type something in, except it's in a girls' voice - which is hilarious," he added.
The 23-year-old singer had the operation at the Massachusetts General Hospital in Boston, earlier this week, reported BBC online.
When asked if Smith's temporary "app voice" might appear in one of his songs, Napes said, "It might be a little outtake on the new album.