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_sharps, that give the number of respective accidentals in a key signature.
#>  "c" "g" "d" "a" "e" "b" "f#" "c#" "f" "b_" "e_" "a_" #>  "d_" "g_" "c_" "am" "em" "bm" "f#m" "c#m" "g#m" "d#m" "a#m" "dm" #>  "gm" "cm" "fm" "b_m" "e_m" "a_m"
#>  TRUE
#>  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
#> <Noteworthy string> #> Format: space-delimited time #> Values: a, b, 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
#> <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_ c' d' e'
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
#>  "ionian" "dorian" "phrygian" "lydian" "mixolydian" #>  "aeolian" "locrian"
#> <Noteworthy string> #> Format: vectorized time #> Values: c d e_ f g a_ b_
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_,dfa> <ce_gb_> <dfac'> <e_gb_d'> <fac'e_'> <gb_d'f'> <ac'e_'g'>
#> <Noteworthy string> #> Format: space-delimited time #> Values: <f#ac#'> <g#bd'> <ac#'e'> <bd'f#'> <c#'e'g#'> <d'f#'a'> <e'g#'b'>
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.
NA is also used when rests occur. Octaves are ignored. For
scale_note, degrees outside the range of the scale are recycled. See below. To see if chords are fully diatonic, use
is_diatonic or the more general
chord_degree will return a list comparable to
#>  1 3 2
#>  NA 5 4
#>  3 5 4
#>  1 5 3
#> <Noteworthy string> #> Format: vectorized time #> Values: d e f# g a b c#
#> <Noteworthy string> #> Format: vectorized time #> Values: d e f g a b_ d_ d
#>  TRUE TRUE
#> [] #>  NA #> #> [] #>  1 #> #> [] #>  1 NA 5 #> #> [] #>  1 3 5 #> #> [] #>  3 5 7
#>  NA TRUE FALSE TRUE TRUE
#>  NA TRUE FALSE TRUE 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 fourth 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
#>  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. It is vectorized and both inputs must have the same number of timesteps.
Chords can be reduced to their root note (lowest pitch) for comparison or forced to yield an
NA interval with respect to its two adjacent timesteps (e.g.,
NA and so is
r and silent rests
s also yield an
NA for the interval from a prior note.
#>  3
#>  0 -2 -4
#>  NA 0 2 2 2 2 NA
#>  NA 0 NA 2 2 2 NA
scale_interval. This function is similar to
pitch_interval in that it takes two noteworthy strings, which together define an intervals element-wise. It is almost an inverse of
interval_semitones except that you provide notes rather than the semitone distance of their intervals. The function returns a main interval name or abbreviation from
mainIntervals, depending on
format. The results are name-only. They are not signed. Use
pitch_interval to obtain direction.
#>  "P8" "M3" "P5" "M7"
#>  "minor third"
There are also lagged difference versions of these functions. You can adjust the lag with
n. You can also retain (convenient for data frames) or trim the
NAs. This does not trim meaningful
NAs like those resulting from rests.
#>  NA 2 2 1 2 2 2
#>  2 2 1 2 2 2
#>  NA "M2" "M2" "m2" "M2" "M2" "M2"
#>  NA NA "M3" "m3" "m3" "M3" "M3"
Lagged intervals respect rest timesteps. All timestep positions including rests are retained, but the lag-
n difference computation ignores them.
#>  NA 3 NA NA NA NA 7
#>  NA "m3" NA NA NA NA "P5"
#>  NA NA NA NA NA NA 10
#>  NA NA NA NA "m7"