tabr

Author: Matthew Leonawicz License: MIT

Overview

The tabr package provides a music notation syntax and a collection of music programming functions for generating, manipulating, organizing and analyzing musical information in R. The music notation framework facilitates creating and analyzing music data in notation form.

Music programming in the notation syntax provided by tabr can be used for a variety of purposes, but it also integrates cohesively with the package’s transcription functions. The package also provides API wrapper functions for transcribing music notation in R into guitar tablature (“tabs”) using LilyPond.

LilyPond is an open source music engraving program for generating high quality sheet music based on markup syntax. tabr generates LilyPond files from R code and can pass them to LilyPond to be rendered into sheet music pdf files from R. While LilyPond caters to sheet music in general and tabr can be used to create basic sheet music, the transcription functions focus on leveraging LilyPond specifically for creating quality guitar tablature.

While LilyPond is listed as a system requirement for tabr, you can use many package functions without installing LilyPond if you do not intend to render tabs.

Use case considerations

tabr offers a useful but limited LilyPond API and is not intended to access all LilyPond functionality from R, nor is transcription via the API the entire scope of tabr. If you are only creating sheet music on a case by case basis, write your own LilyPond files manually. There is no need to use tabr or limit yourself to its existing LilyPond API or it’s guitar tablature focus.

However, if you are generating music notation programmatically, tabr provides the ability to do so in R and offers the added benefit of converting what you write in R code to the LilyPond file format to be rendered as printable sheet music.

With ongoing development, the music programming side of tabr will likely continue to grow much more than the transcription functionality.

Why LilyPond for transcription?

LilyPond is an exceptional sheet music engraving program.

• It produces professional, high quality output.
• It is open source.
• It offers a command line access point for a programmatic approach to music notation.
• It is developed and utilized by a large community.
• Most GUI-based applications are WYSIWYG and force a greater limitation on what you can do and what it will look like after you do it. It is only for the better that tabr is the bottleneck in transcription limitations rather than the music engraving software it wraps around.

Functionality and support

The tabr package offers the following:

• Render guitar tablature and sheet music to pdf or png.
• Write accompanying MIDI files that can respect repeat notation and transposition in the sheet music (under reasonable conditions).
• Support tablature for other string instruments besides guitar such as bass or banjo.
• Support for instruments with different numbers of strings.
• Support for arbitrary instrument tuning.
• Offers inclusion (or exclusion) of formal music staves above tab staves, such as treble and bass clef staves for complete rhythm and timing information.
• If music staff is included, the tab staff can be suppressed, e.g., for vocal tracks.
• Track-specific setup for features like instrument type, tuning and supplemental music staves.
• Provides common notation such as slide, bend, hammer on, pull off, slur, tie, staccato, dotted notes, visible and silent rests.
• Allows arbitrary tuplet structure.
• Above-staff text annotation.
• Percent and volta repeat section notation.
• Note transposition.
• Staff transposition.
• Multiple voices per track and multiple tracks per score.
• Chord symbols above staff
• Chord fretboard diagrams and chord chart at top of score.
• A variety of layout control options covering settings from score attributions to font size.
• Optional alternative input format allowing the user to provide string/fret combinations (along with key signature and instrument tuning) to map to pitch.

Installation

You can install tabr from CRAN with:

install.packages("tabr")

You can install tabr from GitHub with:

# install.packages("remotes")
remotes::install_github("leonawicz/tabr")

Noteworthy strings

As a quick introduction and to get oriented to the music notation syntax offered by tabr, consider the concept of a noteworthy string. This is like any other character string, except that what makes a string noteworthy is that its content consists strictly of valid tabr music notation syntax. It can be parsed unambiguously and meaningfully into a musical phrase (see next section) and can be processed as input to the various package functions that inspect and manipulate musical information.

A simple character string like "c e g", or alternatively as a vector, c("c", "e", "g"), is a noteworthy string. Even "a" is noteworthy. So are "a#" and "a_" (sharp and flat). However, "A" is not, nor is "Z". There are other pieces of valid syntax than just the lowercase letters a through g and sharp and flat notation. See the package vignettes for details.

Noteworthiness can be checked on any character string. No supplemental class is required. When defining noteworthy strings you can define them like any other character vector. However, you will notice that package functions that operate on noteworthy strings and whose output is another noteworthy string will yield a string with the supplemental noteworthy class. This has its own print and summary methods. If you remove the class with a common R operation like as.character(), it does not impact any subsequent musical manipulation beyond the need to reperform a noteworthy check.

x <- "g#4 c5 d#5 g#4c5d#5"
as_noteworthy(x)
#> <Noteworthy string>
#>   Format: space-delimited time
#>   Values: g#4 c5 d#5 <g#4c5d#5>

is_note(x)
#> [1]  TRUE  TRUE  TRUE FALSE
is_chord(x)
#> [1] FALSE FALSE FALSE  TRUE
chord_is_major(x)
#> [1]   NA   NA   NA TRUE
(x <- transpose(x, 1))
#> <Noteworthy string>
#>   Format: space-delimited time
#>   Values: a4 c#5 e5 <a4c#5e5>

summary(x)
#> <Noteworthy string>
#>   Timesteps: 4 (3 notes, 1 chord)
#>   Octaves: integer
#>   Accidentals: sharp
#>   Format: space-delimited time
#>   Values: a4 c#5 e5 <a4c#5e5>

distinct_pitches(x)
#> <Noteworthy string>
#>   Format: space-delimited time
#>   Values: a4 c#5 e5
distinct_pitches(x) %>% pitch_freq() # in Hz
#> [1] 440.0000 554.3653 659.2551

tabr offers many functions for manipulating musical structures defined in music notation. See the vignettes for more information on music programming.

Basic transcription example

Rendering sheet music is based on building up pieces of musical information culminating in a score. The fundamental object to consider in the transcription context is a phrase. A phrase is created from a noteworthy string and incorporates additional information, most importantly time and rhythm. It can also include positional information such as the instrument string on which a note is played. Outside of rendering tabs, there is no reason to construct phrase objects. Everything from the phrase object on up is about using the R to LilyPond pipeline to render some kind of sheet music document.

If you doing music analysis on noteworthy strings and are combining the note, pitch or chord information with time, that can be done with a corresponding variable; using a phrase object is not the way to do that because phrase objects are intended for the construction of LilyPond markup syntax.

As a brief example, recreate the tablature shown in the image above (minus the R logo). Here are the steps.

• Define a musical phrase with phrase or the shorthand alias p.
• Add the phrase to a track.
• Add the track to a score.
• Render the score to pdf with tab.

The code is shown below, but first some context.

Constructing a musical phrase

A phrase here does not require a strict definition. Think of it as the smallest piece of musical structure you intend to string together. The first argument to phrase is a string describing notes of a specific pitch (or rests: “r”), separated in time by spaces. For chords, just remove spaces to indicate simultaneous notes. Integers are appended to indicate the octave number so that the pitch is unambiguous. For example, a rest followed by a sequence of notes might be given by notes = "r a2 c3 f3 d3 a3 f3".

The second argument is a similar string giving note metadata. In this example there is nothing to add but the time durations. Whole notes taking up an entire measure of music are given by 1, half notes by 2, quarter notes 4, eighth notes 8, and so on. To specify a quarter note rest followed by a sequence of eighth notes, use info = "4 8 8 8 8 8 8" (or shorten to just info = "4 8*6"). This basic example does not require specifying additional note information such as dotted notes for different fractions of time, staccato notes, ties/slurs, slides, bends, hammer ons and pull offs, etc. These specifications are currently available in tabr to varying degrees of development and are covered in the vignette tutorials.

The third argument, string, is optional but generally important for guitar tablature. In similar format, it specifies the strings of the guitar on which notes are played. Providing this information fixes the fret-string combinations so that LilyPond does not have to guess what position on the neck of the guitar to play a specific note. An inability to specify this in various tablature notation software (or laziness by the user), is a common cause of inaccurate tabs scouring the internet, where even when the notes are correct they are written in the tab suggesting they be played in positions no one would sensibly use. Note that the x shown below is just a placeholder indicating no need to specify a string for the quarter note rest.

The example below employs a couple shortcuts to further reduce typing. The first is to use the * in-string expansion operator mentioned above to avoid typing a long series of eighth notes. Second, it drops explicit reference to octave number three since this central octave is the default octave in LilyPond. This applies to all but the first note below.

While explicit string numbers are not needed for this example, they are provided anyway for full context. Dropping the string argument would further reduce typing.

Score metadata and accessing LilyPond

Finally, specify some song metadata to reproduce the original staff: the key of D minor, common time, and the tempo.

If LilyPond is installed on your system (and added to your system path variable on Windows systems), tab should call it successfully. Windows users are recommended to just add LilyPond’s bin directory to the system path. This will take care of LilyPond as well as its bundled Python and MIDI support. As an example for Windows users, if the LilyPond executable is at C:/Program Files (x86)/LilyPond/usr/bin/lilypond.exe, then add C:/Program Files (x86)/LilyPond/usr/bin to the system path.

R code

library(tabr)

p("r a2 c f d a f", "4 8*6", "x 5 5 4 4 3 4") %>% track %>% score %>%
  tab("phrase.pdf", key = "dm", time = "4/4", tempo = "4 = 120")

#> #### Engraving score to phrase.pdf ####
#> GNU LilyPond 2.18.2
#> Processing `./phrase.ly'
#> Parsing...
#> Interpreting music...
#> Preprocessing graphical objects...
#> Interpreting music...
#> MIDI output to `./phrase.mid'...
#> Finding the ideal number of pages...
#> Fitting music on 1 page...
#> Drawing systems...
#> Layout output to `./phrase.ps'...
#> Converting to `./phrase.pdf'...
#> Success: compilation successfully completed

For comparison, if you were using string-fret specification to construct the above phrase, one way to do so is the following:

sfp("r;r;4 5;0;8 3 4;3; 0 3;2; 4;3;")
#> <Musical phrase>
#> r4 <a,\5>8 <c\5>8 <f\4>8 <d\4>8 <a\3>8 <f\4>8

It may not look particularly beneficial here, but for more complex music it can be easier to reason about the phrase under construction when using this format to bind information by time step rather. See ?sf_phrase for a comparison with phrase and the various ways you can do phrase construction in tabr for equivalent results. If you are looking to do quick, easy and basic tabbing, you may want to consider using the single-argument input method of the sf_phrase function. The package vignettes focus on general use cases using the phrase function rather than sf_phrase.

Note above that tabr also exports the pipe %>% operator. Even given the hierarchy of objects involved in the series of steps to move from a phrase to a rendered pdf, a short example like this does not even require a single assignment. While music can be quite complex and a full score will be much longer, tabr strives to minimize the work while still forcing some sense of interpretable, organized structure. For long and complex music, it can require some effort and practice to ensure your approach to transcription in your R code is not opaque.

References and resources

There are several vignette tutorials and examples at the tabr website.

R-Music

R for music data extraction and analysis

See the R-Music organization on GitHub for more R packages related to music data extraction and analysis. The R-Music blog provides package introductions and examples.

Other packages

• The tuneR package for analysis of music and speech by Uwe Ligges, Sebastian Krey, Olaf Mersmann, and Sarah Schnackenberg.

Please note that this project is released with a Contributor Code of Conduct. By participating in this project you agree to abide by its terms.