This section introduces the use of chords in tabr. All
of the functionality surrounding individual notes in phrases generalizes
to chords. Chords symbols can also be displayed above sheet music staves
and chord diagrams can be included at the top of sheet music scores
using a chord chart. These topics are covered in the subsequent section
on tracks and scores. This section here focuses on using chords in
phrase() where their notation will become part of the
content engraved in the sheet music staves.
Chord syntax
Like individual pitches, chords and other combinations of simultaneous pitches can be specified in multiple equivalent ways. The only difference is that there are no spaces between the notes. The following are equivalent ways to specify the same open C major chord. This is shown for completeness, but remember that octave tick format should be used; number format has limited utility in other contexts.
phrase("cegc'e' c3e3g3c4e4 cegc4e4", 4)#> <Musical phrase>
#> <c e g c' e'>4 <c e g c' e'>4 <c e g c' e'>4When the notes of a chord are tied over to the next, it is convenient
to use tie() to avoid having to write the ~
explicitly for each note in the chord.
tie("cegc'e'")#> <Noteworthy string>
#> Format: space-delimited time
#> Values: <c~e~g~c'~e'~>Similar to notes, explicit string numbers passed to the
string argument also remove spaces between individual
string numbers. Recall the inferred strings when only the first (lowest
number) string is given, as well as the expansion operator. Recycling
only works when it is a single value.
chords <- "cegc'e' c3e3g3c4e4 cegc4e4"
x <- phrase(chords, 4, "54321 54321 54321")
identical(phrase(chords, 4, "5*3"), x)#> [1] TRUE#> [1] TRUEChord syntax for fretboard diagrams
Chord diagrams refer to the fretboard diagrams commonly displayed in
sheet music written for guitar. These chord diagram specifications are
passed to score(), discussed in the next section that
brings together the overall process of moving from phrases to tracks to
a score. Here, the syntax used to specify chords for chord diagrams is
introduced. Below are some chords that appear in a song.
Note that minor chord names, indicated by m, are one of
the available chord modifiers. These modifiers come after the separator
:. This is different from how key signatures can be
expressed throughout most of tabr, with just a
"dm" for example, but the modifiers that follow the colon
have more general uses for chord diagrams. There will be more examples
of this in a moment.
The chords also require position descriptions, because the same chord
can be played many ways. This is the part that fully defines the chord
diagram. As is standard, x means a string is not played and
o refers to an open string. The numbers refer to the fret.
The string is six characters representing strings six through one (low
to high pitch) from left to right.
chord_names <- c("d:m", "f", "g:m", "a")
chord_positions <- c("xxo231", "133211", "355333", "xo222o")Named vector input
If the chord positions are a named vector, there is no need to pass
both positions and names separately to chord_set(). It will
check the first argument for names before looking to the second
argument.
chords <- chord_set(chord_positions, chord_names)
chords#> d:m f g:m a
#> "x;x;o;2;3;1;" "1;3;3;2;1;1;" "3;5;5;3;3;3;" "x;o;2;2;2;o;"#> [1] TRUEAnalogous to phrase(), chord_set() is a
simple function that manipulates the input strings into a named
character vector of chord entries in a format understood by
LilyPond.
Chord chart
Next, to demonstrate the chord chart, make a dummy song and include the chord set. The output for the dummy song now contains a chord chart centered at the top of the first page of sheet music.
Details
The next example highlights several facts about chord specification for fretboard diagrams and chord charts.
- There are other chord modifiers besides the common
mthat follow the:separator including chords such as suspended second and forth chords. See the first two chords below. Common modifiers includem,7,m7,dim,dim7,maj7,6,sus2,sus4,aug,9. - Chord inversions, or simply any chord described as a chord combined
with some alternate bass or root note, are examples of chords notated
with a
/<note>. This is suffixed to the the chord regardless of whether that places it against an otherwise unmodified chord or after a chord modifier. See the next two chords below. - Leading
xis inferred. See below. Chords including 2-digit fret numbers require using spaces or semicolons as a delimiter. Do not mix the two. See the fifth chord below. - The same chord name can be assigned to different chord positions. See the next two chords below, both D minor.
- Number of strings on the instrument is inferred from the number of
entries in the chord string. However, there is not currently support for
different numbers of strings. See the final chord below, which attempts
to add a seventh (unplayed) string, duplicating the first Asus2 chord.
The
xis marked in the output, but no string appears. Similarly, if fewer strings are indicated by the fret positions provided, such as for an instrument with fewer than six strings, this results in erroneously applying them to a subset of the six guitar strings in the fretboard diagram. More general support may come later. - If a chord vector used for other purposes (see next section on chord
sequences) happens to contain
rorsentries for rests or silent rests, they are passed through bychord_set()but ignored when generating chord charts. - The chord chart displays chords in the order they were defined.
chords <- c("xo22oo", "o223o", "xxx565", "786", "10 10 10 8", "o231", "765", "o22oo", NA, NA)
names(chords) <- c("a:sus2", "a:sus4", "f/c", "g:m/d", "f", "d:m", "d:m", "a:sus2", "r", "s")
chords <- chord_set(chords)
p("r", 1) |> track() |> score(chords) |> tab("ex14.pdf")
Chord symbols and sequences
You have already seen chord symbols, placed above the fretboard
diagrams above. Chord symbols refer to the shorthand chord notation, or
chord labels, often shown above chord diagrams as well as above a music
staff at the beginning of measures or at each chord change. These are
the familiar labels such as C Dm F# F/C. The next use of
chords is placement above the staff in time. This is the chord
sequence.
In order to place chord symbols in time above a music staff, it is necessary to specify their sequence and the duration of each chord, just like is required for all the notes and chords shown inside the staff that are created from a sequence of phrase objects. The two examples below uses a simple melody of arpeggiated, broken chords played using the chords C, F and G. Those chord symbols are shown above the staff at the appropriate point in time based on the defined chord sequence.
notes <- "c e g c' e' c' g e g b d' g' f a c' f' c e g e c"
info <- c("8*20 2", "4*20 1")
strings <- pc(c(5:1, 2:4, 4:1, 4:1, 5:3, 4:5)) # almost not needed, but for 1st 2 notes of G chord
p1 <- p(notes, info[1], strings)
p2 <- p(notes, info[2], strings)
chords <- chord_set(c(c = "32o1o", f = "3211", g = "5433", r = NA, s = NA))Chord sequence
In the first version, there is a chord change halfway through a
measure. Assign beat duration information for each chord in the sequence
just as you would with the info argument to
phrase(), e.g., half a measure is given with
2. The C chord is played for a full measure both times
while the F and G chords each last half a measure. The chord sequence is
named just like chords above. This is how the correct chord
symbol is applied above the staff at the correct time. Taking the names
directly from chords as a chord dictionary for the song is
the suggested way to avoid having to type chord symbols repeatedly.
Finally, score() takes a chord_seq argument
after the chords argument. Building on the previous
example, here both are passed to score().
chord_seq <- c(1, 2, 2, 1)
names(chord_seq) <- names(chords)[c(1, 3:1)] # C G F C
track(p1) |> score(chords, chord_seq) |> tab("ex15.pdf")
Using rests
Version two double the duration of all notes. Now the C chord lasts
for two full measures while the F and G chords are played for one
measure each. You can always specify a chord for every measure, in this
case providing the C chord in the sequence twice in a row for one
measure each. However, this example uses rests. Note the inclusion of
r and s in the current chords
vector.
To illustrate how rests factor into chord sequences, a silent rest is
used for measure two. This avoids showing the C chord twice in a row
without a chord change in between. Nothing is shown above the staff at
this point in time. The final measure of the phrase uses a regular rest,
which is not silent. This leads to the “no chord” symbol
N.C. being printed above the staff. You do not show a chord
as lasting longer than a measure by providing values less than one. This
example also shows a very simple but also very common case where a song
does have every chord in its chord sequence last for exactly one
measure.
chord_seq <- rep(1, 6)
names(chord_seq) <- names(chords)[c(1, 5, 3:1, 4)] # C (s) G F C (r)
track(p2) |> score(chords, chord_seq) |> tab("ex16.pdf")
Overall picture
Since the chord chart is included and was only shown in prior examples zoomed in, here is the result above showing the full sheet, which includes the staves and chord symbols, the chord chart positioned top center, and for perspective the page numbering in the top right corner.
To sum up, chords are used in tabr in three ways. Using
phrase(), they appear among other notes in staves as the
core component of the music transcription. They are also used by
score() to generate chord charts using fretboard diagrams
that summarize all the chords that occur in a song. Finally, the same
chord symbols can be listed in sequence with corresponding durations to
be applied above a music staff, showing the chord progression throughout
the song in proper time.