There are a number of functions that assist with music programming around note and pitch validation, comparison, equivalence checking, and various manipulations and transformations. In a previous section, you saw is_note
and is_chord
. Other identity functions include:
#> [1] TRUE FALSE TRUE FALSE
#> [1] FALSE TRUE FALSE TRUE
#> [1] FALSE TRUE FALSE TRUE
#> [1] FALSE FALSE FALSE FALSE
These note_is_*
functions strictly accept notes. There is also is_diatonic
, which less strictly requires any noteworthy string. It can be applied to notes and chords alike. Given the name, it is slightly less basic than the prior functions. It takes a key
signature for context.
#> [1] TRUE FALSE TRUE FALSE FALSE
#> [1] TRUE TRUE TRUE TRUE FALSE
Note that it is common for functions like this to treat notes as different if they sound the same but one is transcribed as a flat and the other as a sharp. tabr
does focus on transcription and this is an important distinction to make wherever necessary. Other functions such as transpose
of course handle pitch as pitch and therefore the style of representation does not affect computation.
There are functions for enforcing a singular representation for accidentals in noteworthy strings since it is unusual to mix flats and sharps.
#> <Noteworthy string>
#> Format: space-delimited time
#> Values: c e_ g b_ <ce_g>
#> <Noteworthy string>
#> Format: space-delimited time
#> Values: c d# g a# <cd#g>
Do not be confused about the names of these functions. They are for enforcing a single type of accidental. To actually lower sharps by a half step or semitone as well as raise flats similarly, use naturalize
.
#> <Noteworthy string>
#> Format: space-delimited time
#> Values: c e g b <cdg>
These are helpful building blocks for music programming. A useful wrapper around flatten_sharp
and sharpen_flat
is note_set_key
. Like is_diatonic
, this function takes a key
argument. Providing a key signature is often used in tabr
functions for the purpose of enforcing the correct representation of accidentals intended by the user, which tabr
cannot know until informed.
Be aware that the default for functions that take a key
argument is c
, but c
and am
have no accidentals in their key signatures, so note_set_key
will have no effect if you pass these values to key
. It is also important to recognize that it does not matter for this function what key you choose specifically; it only matters that you choose a key that has the type of accidentals in its signature that you wish to force your noteworthy string to use. If you want flats, it makes no difference if you set key = "f"
or key = "b_"
. For this function, you can also literally enter key = "flat"
or key = "sharp"
, options that stress the extent to which key
actually matters to note_set_key
.
#> <Noteworthy string>
#> Format: space-delimited time
#> Values: c e_ g b_ <cd#g>
#> <Noteworthy string>
#> Format: space-delimited time
#> Values: c e_ g b_ <ce_g>
#> <Noteworthy string>
#> Format: space-delimited time
#> Values: c d# g a# <cd#g>
The intent is not to force notes which may not be diatonic to the key signature to fit that signature. All pitches remain exactly what they are. It does not matter if they are not in the key. But they are forced to conform to a key’s representation of accidentals.
Of course, for many other functions in tabr
, key
arguments utilize the specific key signature in a more complete manner, and the options flat
and sharp
are not relevant or allowed.
The note_is_*
functions mentioned earlier are vectorized, but the operations they perform are self checks. Other functions are available for comparative checks of identity or equivalence between two notes. These functions are also vectorized. Each note input can be an entire noteworthy string.
There are different dimensions along which the strictness of equality varies and are worth taking a moment to break these and other properties down clearly:
*_is_equal
and *is_identical
pairs. Equality is more relaxed than identity.note_is_*
pairs below also offer the argument ignore_octave
. This further weakens the requirements for passing both equality and identity comparisons of two notes.e_
and d#
, they are equal, but not identical.octave_is_*
pairs.First look at note and pitch comparisons. The main difference is that pitch is more complete than note in that the former implicitly carries the octave position. Setting ignore_octave = FALSE
for note comparisons makes them equivalent to their pitch comparison counterparts.
#> [1] TRUE TRUE
#> [1] TRUE FALSE
#> [1] FALSE TRUE
#> [1] FALSE FALSE
There are minimal requirements for equivalence that precede the forms and degrees of equivalence described and shown above. At a bare minimum, two noteworthy strings must have the same number of time steps available for pairwise comparison. Otherwise a simple NA
is returned. In the following example, the strings x
and y
have the same number of notes, in the same order, but the first has three times steps and the second has two.
#> [1] NA
In the next example, x
and y
have the same number of of the same notes, again in the same order, and even have an equal number of timesteps. Having the same number of timesteps makes pairwise comparisons possible. They return FALSE
where unequal.
#> [1] TRUE FALSE FALSE
Finally, there are octave comparisons, which must be defined and behave somewhat differently. octave_is_equal
and octave_is_identical
allow much weaker forms of equivalence in that they ignore notes completely. These functions are only concerned with comparing the octave numbers spanned by any pitches present at each timestep.
When checking for equality, octave_is_equal
only looks at the octave number associated with the first note at each step, e.g., only the root note of a chord. octave_is_identical
compares all octaves spanned at a given timestep by considering all notes when a chord is present.
This still leaves open the definitions of equivalence. To clarify:
Consider an example: a1b2c3
is identical to d1e1f2g3
. The notes are irrelevant. The number of notes is irrelevant. The fact that octave number one occurs a different number of times in each chord is irrelevant. What matters is that they both have the same set of unique octave positions {1, 2, 3}
. To be equal, even less is required. In this case it only matters that the two chords begin with x1
, where x
is any note.
One alternative, for octave_is_identical
only, is to set single_octave = TRUE
. This increases the requirement for identity to require that all notes from both chords being compared at a given timestep share a single octave.
#> [1] FALSE TRUE TRUE TRUE TRUE
#> [1] FALSE TRUE TRUE FALSE TRUE
#> [1] FALSE TRUE FALSE FALSE TRUE
Rotating or cycling a sequence of notes and chords in a noteworthy string is done with note_rotate
. This is a simple function. It only rotates the sequence left or right. It does not do any transposition. It does not break chords, but rather rotates them intact.
#> <Noteworthy string>
#> Format: space-delimited time
#> Values: b <ceg> a
#> <Noteworthy string>
#> Format: space-delimited time
#> Values: <ceg> a b
note_shft
only operates on notes, not chords, but is a more complex function. It also rotates notes, but it maintains a consistent direction of increasing or decreasing pitch. The direction is determined by n
being negative or positive.
This function is intended for use on strings of notes that are already ordered by increasing pitch. However, if applied to a sequence of unordered notes, the sequence will eventually become ordered if n
is large enough, because each shift transposes the current lowest note by however many full octaves necessary to be above the current highest note and as close to it as possible.
#> <Noteworthy string>
#> Format: space-delimited time
#> Values: e g c4
#> <Noteworthy string>
#> Format: space-delimited time
#> Values: g1 c2 e2
note_arpeggiate
is like note_shift
but it extends the original note sequence rather than shifting it and maintaining its fixed size. n
refers to the number of additional notes to append to the sequence. The length of the final sequence is the length of the original sequence plus n
.
#> <Noteworthy string>
#> Format: space-delimited time
#> Values: c e g c4 e4 g4 c5 e5
#> <Noteworthy string>
#> Format: space-delimited time
#> Values: e1 g1 c2 e2 g2 c e g
The next section on music programming covers various helper functions related to chords.