Lilypond chord mode not rendering minor modifier in alternate chord

Question

I'm engraving some music using Lilypond and have been requested to engrave an alternate chord name next to a chord. For some reason I can't get the output I expected. What is wrong here (with either my Lilypond code or the music notation)?

    Chords = \chordmode {
      d2:m/f c/e:m 
    }

This produces something like this:

Dm/F C/E

But I was expecting this:

Dm/F C/Em

There is an warning thrown to the console that says:

Parsing...  
warning: Spurious garbage following chord: (chord-colon #<procedure minor-modifier (pitches)>)

Clearly it isn't happy with this notation, but even having reviewed the manual on Chord notation I don't see a reason this wouldn't work. Is there a proper way to notate this?

Edit: As best I can make out at this time the musician expected the guitar player to normally play one chord but that a piano player playing the same thing might optionally use a different chord. Some sort of optional substitution. Rather than having different scores they'd just been notating this in pencil with a sash and the other possible chord for that location. Is there a more proper notation for such a situation?

Answer 1

The problem is that this is not a common notation, and the meaning of the symbol "C/Em" is unclear. What Lilypond can do - as you know - is add a letter after a slash, e.g. C/E, which means that you're supposed to play a C major triad with the note E in the bass.

What does exist are polychords where two different chords are stacked on top of each other. However, this is usually indicated by a horizontal line separating the two chord symbols. But I'm pretty sure that the notation C/Em does not imply a polychord with a C triad on top of an Em triad, simply because these two chords share two of their three notes, so such a polychord hardly makes any sense.

If it is, as you seem to believe, a substitute chord (probably Em replacing C major) then you could simply just write "Em" without mentioning the C chord at all. That's commonly done when substituting chords. The sheet music doesn't need to show which chord was substituted, just which chord has to be played. If the notation is supposed to leave the choice of the chord up to the musician, then I would suggest to write "C (Em)" or "Em (C)". The parentheses make it clear that the other chord is an option. I must add, however, that this is not very common, and just makes the reading more difficult. Musicians either want to play what's written (without thinking too much), or they know what they're doing anyway, and choose appropriate substitution chords themselves.

By the way, if you think that both chords should sound simultaneously (as I've just read in your edited question), possibly played by different instruments, then it would make sense to unify those two chords into one chord: C+Em = Cmaj7. The Cmaj7 chord has all four different chord tones of the C and Em triads: C E G (C major triad) + E G B (Em triad) = C E G B (C major seven chord).

I suggest that as long as the intended meaning of the symbol "C/Em" is unclear, it is useless to discuss how to engrave it. Given the intended meaning, you can come up with the most common typographic options, and only then will it make sense to investigate which of these options can be realized using Lilypond.

Answer 2

Like the other answers, I don't know what your notation is supposed to mean, but you can get (almost) anything you want using "chord name exceptions" to define your own markup.

To repeat, I have no idea if the notes c e g b are what your chord notation is supposed to mean - but if you only want chord symbols, the notes don't matter much.

\version "2.18.2"
% Define the notes in the chord and the markup following the basic chord name 
% i.e. C in this example

chExceptionMusic = { <c e g b>-\markup { / Em } }

% Magic incantation copied from the Lilypond documentation

chExceptions = #( append
  ( sequential-music-to-chord-exceptions chExceptionMusic #t)
  ignatzekExceptions)

% Define some chords

theMusic = { \chordmode { c1 c/e
% insert our weird chord notation
\set chordNameExceptions = #chExceptions c:maj7
% restore normality
\unset chordNameExceptions c:maj7 } }

% Create the score

<< \context ChordNames \theMusic
    \context Voice \theMusic
>>