[sorbus]

Entirely computers. Hatsune Miku and similar software are basically voice synthesizers geared towards music, as I understand it, not hugely unlike other text-to-speech programs but with more control of pitch, tone, and so forth.

Also, as far as making artificial intelligences compose and perform, it might be interesting to hook up Hatsune Miku to a Markov chain generator[1], and feed it a bunch of j-pop as input. Would probably take some fine-tuning and modification to get it to give output that the synthesizer would understand (as it would be dealing with both words and notes), but it's not too far fetched.

[1] Which isn't an AI by any means, being more of way of generating text based on statistical correlations between words in the input body of data, but it comes up with some rather interesting things.