A livestreamed Metallica performance via Twitch went hilariously off the rails, through no fault of the band.

The iconic metal group was performing a set for this year’s BlizzCon video game convention, which was being broadcast to the masses on Friday via the Twitch app.

Just as the band kicked off a song, frontman James Hetfield hits a few chords before the music the band is producing suddenly stops, replaced by a generic copyright-free song featuring accordion and glockenspiel, while the band continued to play.

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Twitch has been hit by several complaints in the past over hosting content that violates the Digital Millennium Copyright Act, and substituted the music in an apparent overabundance of caution — even though, if Twitch were to be sued, it would be by Metallica.

According to Eurogamer, the glitch was likely the work of a bot that automatically made the substitution; it occurred on just one of the channels that was hosting the feed, the Twitch Gaming channel, with the performance streaming uninterrupted on the other channels, including Blizzard’s Twitch channels and on YouTube.

Some fans couldn’t help point out the irony that it was Metallica’s 2000 lawsuit against Napster that was instrumental in the very legislation that led Twitch to replace the sound feed with generic music.

Meanwhile, here’s a sampling of how fans reacted on social media to the copyright-protecting switcheroo.