Piano chart

library(pichor)

There is built-in data in keys_chords with information about some of the keys on a piano. These can be used for e.g. drawing a diagram of a piano:

ggpiano(keys_chords)

It is also possible to highlight certain keys (and show labels):

keys_chords_highlighted <- highlight_keys(keys_chords, keys = c(7, 10, 14))
ggpiano(keys_chords_highlighted, labels = TRUE)

The above is also possible using magrittr’s pipe, %>%:

library(magrittr)

keys_chords %>% 
  highlight_keys(keys = c(7, 10, 14)) %>% 
  ggpiano(labels = TRUE)

Working with chords

It is possible to work with chords, e.g. getting keys, the highest tone etc.:

chrd <- construct_chord_raw(root_tone = "F#", distances_rel = c(4, 3))
chrd
## F# chord with tones F#/Gb, A#/Bb, C#/Db
as.character(chrd, brief = TRUE)
## [1] "F#"
chrd_Fsm <- construct_chord_minor(root_tone = "F#")
chrd_Fsm
## F#m chord (minor) with tones F#/Gb, A, C#/Db
as.character(chrd_Fsm)
## [1] "F#m chord (minor) with tones F#/Gb, A, C#/Db"
as.character(chrd_Fsm, brief = TRUE)
## [1] "F#m"
get_keys(chord = chrd_Fsm)
## [1]  7 10 14
get_keys_highest_tone(chord = chrd_Fsm, highest_tone = "A")
## [1]  2  7 10

And instead of highlight keys, chords can be highlighted, too:

keys_coords %>% 
  highlight_chord(chord = chrd_Fsm) %>%  # root form by default
  ggpiano()

keys_coords %>% 
  highlight_chord(chord = chrd_Fsm, highest_tone = "A") %>% 
  ggpiano()

It is also possible to work with chord inversions:

chrd_Bm <- construct_chord_minor(root_tone = "B")
get_keys(chord = chrd_Bm)
## [1] 12 15 19
get_keys_inversion(chord = chrd_Bm, inversion = 0)
## [1] 12 15 19
get_keys_inversion(chord = chrd_Bm, inversion = 1)
## [1]  3  7 12
get_keys_inversion(chord = chrd_Bm, inversion = 2)
## [1]  7 12 15

These can also be highlighted in a chart:

keys_coords %>% 
  highlight_chord(chord = chrd_Bm, inversion = 2L) %>% 
  ggpiano()

Chord sequence

It is also possible to work with a sequence of chords. Let me illustrate it with a version of “Let it be” by Beatles that initially has chords G, D, Em, C, G, D, C.

chords <- list(construct_chord_major("G"),
               construct_chord_major("D"),
               construct_chord_minor("E"), # Em
               construct_chord_major("C"),
               construct_chord_major("G"),
               construct_chord_major("D"),
               construct_chord_major("C"))
chords
## [[1]]
## G chord (major) with tones G, B, D
## 
## [[2]]
## D chord (major) with tones D, F#/Gb, A
## 
## [[3]]
## Em chord (minor) with tones E, G, B
## 
## [[4]]
## C chord (major) with tones C, E, G
## 
## [[5]]
## G chord (major) with tones G, B, D
## 
## [[6]]
## D chord (major) with tones D, F#/Gb, A
## 
## [[7]]
## C chord (major) with tones C, E, G
chord_names <- sapply(chords, as.character, brief = TRUE)
key_seq <- lapply(chords, get_keys)

For more advanced plotting and data wrangling, ggplot2 and dplyr are first loaded. Helpful facet panel titles are providing by sequence_names argument to highlight_key_sequence():

library(ggplot2)
library(dplyr)

keys_chords %>% 
  highlight_key_sequence(key_sequence = key_seq,
                         sequence_names = chord_names) %>% 
  ggpiano() + 
  facet_wrap(~ seq_name)
## NULL

And for example include seq_no in a new column seq_lbl (that are then converted to a factor with the right ordering):

keys_chords %>% 
  highlight_key_sequence(key_sequence = key_seq,
                         sequence_names = chord_names) %>% 
  mutate(seq_lbl = paste0(seq_name, " (#", seq_no, ")")) %>% 
  mutate(seq_lbl = forcats::fct_inorder(seq_lbl)) %>% 
  ggpiano() + 
  facet_wrap(~ seq_lbl)
## NULL

opt_res <- optim_min_dist_exhaustive(key_sequence = key_seq)
keys_chords %>% 
  highlight_key_sequence(key_sequence = opt_res$best,
                         sequence_names = chord_names) %>% 
  ggpiano() + 
  facet_wrap(~ seq_name) +
  labs(title = "Best inversions")
## NULL

keys_chords %>% 
  highlight_key_sequence(key_sequence = opt_res$worst,
                         sequence_names = chord_names) %>% 
  ggpiano() + 
  facet_wrap(~ seq_name) +
  labs(title = "Worst inversions")
## NULL