You only have to hit the notes at the right time and the instrument plays itself JS Bach
Welcome to Box Of Stops, which is a small virtual pipe organ, designed to run on a Raspberry Pi.
Clearly the story of the organ goes back many centuries. Relative to this, the virtual pipe organ is a new entry in this rich history of bellows and pallets. So new there doesn't seem to be an official definition as yet - not even a Wikipedia page at the moment.
The name suggests any organ that wants to sound like it has pipes. For example electronic organs, since the 1930s or so, have been getting better and better at this. Meanwhile others are taking the sound in new and wonderful directions too.
In the computing world, virtual tends to mean an emulation of some kind. Maybe of reality, or even another computer. But something that has been simulated, as opposed to being built from moving parts. Think bits, bytes and pixels, rather than wood, metal and string.
Soon after electronics got good enough to build an organ, they got good enough to build the universal machine that Turing described. This is a versatile invention that is still showing us its abilities decades later. Perhaps inevitably this leads to an expectation - because the computer can do so many things, it is always the best tool for the job.
And often this right, but sometimes there is a case for division of labour here. Especially in the musical world, simpler is often better, and more playable too. If you have a keyboard or synth that can already create quite a refined sound, and a computer that's good at crunching numbers, let's combine these strengths, and have a little fun in the process.