During this question about "China Gates" by John Adams another question came up:

What is the meaning of the little vertical line in bass clef bar 4 in front of the C?

The same mark re-appears several times in the piece, for example in bar 19 in front of an E. Thus, I assume it is not an error.

My first guess was, it was some uncommon accidental, but I could not find it in the related Wikipedia article.

The piece alternates between different modes: A-flat mixolydian, G-sharp aeolian, F lydian and F locrian (source). Could this play a role here somehow?

enter image description here

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    Is it simply a copyist's error or a stray mark on the score?
    – Dekkadeci
    Commented Apr 16, 2018 at 19:43
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    @Dekkadeci The same mark re-appears in bar 19 (see the linked questions). Thus, I thought it's there on purpose.
    – Arsak
    Commented Apr 16, 2018 at 19:48

1 Answer 1


He used that same mark in Phrygian Gates to indicate any time there’s a change in a repetitive pattern. There isn’t enough context in the sample image to tell if that’s the case here, but that’s my assumption. In this case it looks like the main change is the lengths of the Ds and Cs in the pattern.

It’s a pretty nifty and unobtrusive solution to make pattern shifts easier to see within a minimalist or post-minimalist composition.

  • That seems to be the case here as well (googled the first page of the pieces). Do you know, whether this mark is used only by him or is this used in general to highlight pattern shifts?
    – Arsak
    Commented Apr 16, 2018 at 20:25
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    @Marzipanherz I haven’t seen it in any other minimalist composer’s scores, although, in addition to Adams, I’ve only seen scores of Glass, John Luther Adams, Pärt and Gorecki. So I wouldn’t want to answer that question definitively, beyond saying that, so far, I’ve only seen it from him. It’s a weird coincidence, but I actually only got the score for Phrygian Gates a few days ago. Despite not having seen it before, it only took me half a second to realize it’s meaning once I started playing through. My point is, I think it’s clear enough to be safe to use, especially with quick explanation. Commented Apr 16, 2018 at 20:29
  • I'll give it some time before I accept, but I think you've nailed it.
    – Arsak
    Commented Apr 16, 2018 at 20:53
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    I love it when I learn something something completely new. Wish I could give this several more upvotes. Commented Apr 16, 2018 at 21:53
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    @BobBroadley There's always bounties if you really want someone to owe you! Commented Apr 16, 2018 at 21:58

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