Lars Ulrich confirmed that parts of the band’s instrumental track “Orion” was originally intended to be a part of “Sanitarium.”
Asked by Andy Hall on when Metallica decided to separate the two tracks, Lars replied (transcribed by UG):
“I can’t tell you the day and the time and the moment… [Laughs]
“For Metallica making records is very much a practical undertaking. What we do is we’ll have this riff and another riff and those two will live together. And then over here will be this riff and two other riffs, and then over here something else will live and it’s all these different things that we sort of visit.
“So what becomes ‘Battery’ is the fast song. And then over the course of three months we’ll go and work on ‘Battery’ once a week. And every time we go back to it we hopefully take it to another level or hone it or get it more dialed or whatever.
“At some point you sit there and go, ‘Wait a minute, the middle part in ‘Battery’ doesn’t really sound that great in ‘Battery’ but that would actually maybe fit in song number 4.’
“And then you move the parts around. I think the genesis of ‘Orion’ was Cliff Burton’s kind of middle bass part thing with the harmonies and those melodies.
“And we felt that probably should be an instrumental piece. And there was, I think, that main riff that’s at the front half of the song. And somehow we married those together and whatever…
“It’s sort of trial and error and just moving things around. And you’re moving al these pieces of music forward until they become songs that you don’t feel you can better them anymore. [Laughs]
“You get to a place where you don’t feel you can better them anymore and then either they’re so good they go on the record or they go in the trash bin.”
During the rest of the chat, Lars talked about how “The Thing That Should Not Be” came to be, saying:
“We felt we were one song short of a full record. And I guess, ultimately, we sat down with songs that we had, we felt there was a slower, heavier, grindier kind of song that would balance the overall record out.
“So we wrote ‘The Thing That Should Not Be’ in the studio.
“My recollection is that we played a couple of shows here in August of ’85, we played with Scorpions at Day on the Green here in Bay Area, we played the Donington Festival with Bon Jovi, and then we went over and started sort of loading in and getting sounds and setting up and then we wrote ‘The Thing That Should Not Be.’
“Then we went and played a one-off show in Germany called a Lorelai Festival where we world premiered ‘Disposable Heroes.’
“That was like two or three weeks into the recording. And then we went back and continued recording. I think by that time we had written ‘The Thing That Should Not Be’ and we were off and running.”