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Watch Metallica and Lang Lang Rehearse for the Grammys for 21 Minutes

If you like to see Metallica standing around, this is the video for you

Metallica’s performance at the 2014 Grammys was their first at the awards show in 23 years, and they certainly didn’t disappoint. The metal gods ripped through “One” with the aid of Chinese classical pianist Lang Lang, who added complex flourishes to the classic. For posterity’s sake, Metallica also filmed a lot of their rehearsals leading up to the event, and now you can watch the 21-minute long behind-the-scenes cut. Casual fans will probably doze off while James, Lars, Kirk, and Robert discuss the intricacies of their modulations and how many times a bass note is repeated. The best parts are seeing Metallica genuinely awestruck by Lang Lang’s mastery — and Trujillo’s quality bass face.

Check it out above, and head over to iTunes to own the fruits of their labor: “One (Awards Show Rehearsal Version)” is now up for sale, and a portion of the proceeds raised will benefit MusiCares.