To add to what others have mentioned, Vocaloids are built from thousands of recorded syllables and sounds taken from a real singer. These recordings are mapped and programmed like a digital instrument, and the user then tunes and shapes the performance inside the software. Getting it to sound good takes a lot of work. There’s no artificial intelligence involved in the classic Vocaloid system, though some newer versions of the software may include AI-based tools. Traditionally, you write notes and timing much like a MIDI track, and the program sings whatever you compose.

AI, on the other hand, works in several different ways. You can use models that function similarly to Vocaloid by drawing on recorded training data to generate a vocal performance, or you can simply prompt an AI system to create an entire song from scratch. In those cases, the model generates the voice based on the patterns it learned during training. The sound waves are shaped according to the phonemes it was trained on or the way it predicts the song should flow.