Programming with musical scales can be assisted by a collection of functions in tabr
that check and manipulate musical scales, modes and key signatures.
For key signatures, keys
lists valid key signature abbreviation strings for each key as used in tabr
. There are several key_is*
functions that return a logical result regarding properties of keys:
There are also the functions, key_n_flats
and key_n_sharps
, that give the number of respective accidentals in a key signature.
#> [1] "c" "g" "d" "a" "e" "b" "f#" "c#" "f" "b_" "e_"
#> [12] "a_" "d_" "g_" "c_" "am" "em" "bm" "f#m" "c#m" "g#m" "d#m"
#> [23] "a#m" "dm" "gm" "cm" "fm" "b_m" "e_m" "a_m"
#> [1] TRUE
#> [1] 1
The previous section gave an overview of noteworthy strings. While some of the functions that help enforce proper notation in R seemed like they did not offer much utility in terms of direct use, it was clear that they were integral to the robustness of other tabr
functions. Now, looking at these key signature helpers, it may be tempting to dismiss their utility even more quickly because a trained musician does not need to invoke them at the command line to know what result they will return.
These functions are not provided to answer basic questions in an interactive R session so much as they are for programming. These are some of the initial building blocks on top of which more complex functions are built, including many functions in tabr
. As the collection of music programming helper functions in tabr
grows, it becomes easy to do more with less.
Several predefined musical scales are provided and accessible by calling various scale_*
functions.
#> <Noteworthy string>
#> Format: space-delimited time
#> Values: a2 b2 c d# e f g#
You can specify whether the vector result should be returned as is, for convenient vectorized programming pipelines, or collapsed to a single string in keeping with the space-delimited time syntax format common throughout tabr
. Many functions in tabr
accept both formats as inputs and/or offer them as outputs.
You can also specify if octave numbering should be included or stripped. Octave numbering is included by default because this maintains pitch order when the scale does not start on C
. Every note in a noteworthy string has an implicit octave-3 position if not explicitly stated. Octave numbering attempts to be somewhat balanced around C3
. If the result is not what is desired, it can be shifted by 12 semitones with transpose
.
#> <Noteworthy string>
#> Format: space-delimited time
#> Values: f g a b_ c d e
#> <Noteworthy string>
#> Format: space-delimited time
#> Values: f g a b_ c4 d4 e4
See help("scale-helpers")
for details. Depending on the scale, other arguments are available.
The seven modern modes are also available with mode_*
functions or through modern_mode
by passing the mode string name. Other functions include is_mode
and rotate_mode
.
#> [1] "ionian" "dorian" "phrygian" "lydian" "mixolydian"
#> [6] "aeolian" "locrian"
#> <Noteworthy string>
#> Format: vectorized time
#> Values: c d e_ f g a_ b_
The scale_chords
function provides a list of diatonic scale chords based on the root note and scale chosen. It returns triads by default and can also return seventh chords.
#> <Noteworthy string>
#> Format: space-delimited time
#> Values: <b_2dfa> <ce_gb_> <dfac4> <e_gb_d4> <fac4e_4> <gb_d4f4> <ac4e_4g4>
#> <Noteworthy string>
#> Format: space-delimited time
#> Values: <f#ac#4> <g#bd4> <ac#4e4> <bd4f#4> <c#4e4g#4> <d4f#4a4> <e4g#4b4>
The functions scale_note
and scale_degree
map between notes and degree in a given scale. For chords in a noteworthy string, only the root note is considered. For scale_degree
, if a note is not diatonic to the scale, NA
is returned. For scale_note
, degrees outside the range of the scale return NA
.
note_in_scale
can be used to check whether a note is diatonic to a scale. Unlike the other two functions, it strictly accepts single notes. This is more strict that a noteworthy check, which permits chords.
#> [1] 1 3 5
#> [1] NA 5 NA
#> [1] 3 5 7
#> [1] 1 5 8
#> [1] "d" "e" "f#" "g" "a" "b" "c#4"
#> [1] "d" "e" "f" "g" "a" "b_" "d_4" NA
#> [1] TRUE FALSE TRUE
Other functions in tabr
also work with scales and some build upon functions introduced here.
Musical intervals can be referenced by a name or a numeric value defining the separation of two notes. interval_semitones
returns a positive integer describing the number of semitones spanned by a common interval. It takes a name or abbreviation of a common interval as input. Essentially, any entry from any other column in the mainIntervals
dataset can be used to obtain the interval in semitones. It’s a simple filter and match, but it is convenient to map between different representations of the same property in tabr
without typing the extra bit of code to do so each time.
#> # A tibble: 26 x 5
#> semitones mmp mmp_abb ad ad_abb
#> <int> <chr> <chr> <chr> <chr>
#> 1 0 perfect unison P1 diminished second d2
#> 2 1 minor second m2 augmented unison A1
#> 3 2 major second M2 diminished third d3
#> 4 3 minor third m3 augmented second A2
#> 5 4 major third M3 diminished fourth d4
#> 6 5 perfect fourth P4 augmented third A3
#> 7 6 tritone TT diminished fifth/augmented four~ d5/A4
#> 8 7 perfect fifth P5 diminished sixth d6
#> 9 8 minor sixth m6 augmented fifth A5
#> 10 9 major sixth M6 diminished seventh d7
#> # ... with 16 more rows
#> [1] 3 11
Likely more useful for programming, the function pitch_interval
provides the number of semitones between two input notes. This function does not relate to specific scales, but is worth mentioning on the topic of interval helpers. It provides both magnitude and direction. The result is negative if the first note is of higher pitch than the second.
#> [1] -12
#> [1] 3
pitch_interval
accepts a single note for each both note inputs, not sequences, nor chords.
Next is scale_interval
. This function is similar to pitch_interval
in that it takes a note for each of two arguments, which together define an interval. It is almost an inverse of interval_semitones
except that you provide two distinct notes rather than the semitone distance they define. The function returns a main interval name or abbreviation from mainIntervals
, depending on format
.
#> [1] "P8"
#> [1] "minor third"
There is not much else to these interval helper functions, but pitch_interval
is leveraged extensively in support of more complex music programming.