I'm trying to understand what the law says about the use of MIDI or otherwise synthesized representations of songs under copyright within computer games, be they online or installed.
I have read opinions, which make some sense to me, which state that a played back MIDI file counts as an unauthorized performance, albeit by a soundcard, and thus falls under standard copyright law. Is this the case? Does it make any difference at all whether all or part of the representation is performed by a human being, and whether, for example, vocals are replaced by a synth line? Does it make a difference if only a core motif from the song is used as opposed to the full track? And does it make any difference how realistic the sound is - for example, is a bleepy 8 bit rendition any less a violation of copyright than a MIDI file rendered down to a wave file using top-notch orchestral VSTs?
I'm well aware that the digital world is awash with blatant copyright violations and that often it comes down to whether it is worth the copyright holder's effort to enforce the law. But I'm interested to learn exactly what the law is, because this seems like a vague area.