Added methods for synthesising audio

DESCRIPTION

@@ -1,6 +1,6 @@
 Package: hrep
 Title: Harmony Representations
-Version: 0.7.0
+Version: 0.8.0
 Authors@R: person("Peter", "Harrison", email = "pmc.harrison@gmail.com", role = c("aut", "cre"))
 Description: This package provides methods for representing and manipulating chord sequences.
 Depends: R (>= 3.4.0)

NAMESPACE

@@ -137,6 +137,7 @@ S3method(pi_chord_type,pi_chord)
 S3method(pi_chord_type,smooth_spectrum)
 S3method(pi_chord_type,sparse_spectrum)
 S3method(pitch,sparse_pi_spectrum)
+S3method(play_pluck,default)
 S3method(plot,smooth_spectrum)
 S3method(plot,sparse_spectrum)
 S3method(plot,wave)
@@ -161,6 +162,11 @@ S3method(represent,default)
 S3method(represent,list)
 S3method(represent,vec)
 S3method(sample_rate,numeric)
+S3method(save_wav_pluck,coded_vec)
+S3method(save_wav_pluck,default)
+S3method(save_wav_pluck,fr_chord)
+S3method(save_wav_pluck,pi_chord)
+S3method(save_wav_pluck,vec)
 S3method(sparse_fr_spectrum,default)
 S3method(sparse_fr_spectrum,list)
 S3method(sparse_fr_spectrum,pi_chord)
@@ -254,8 +260,10 @@ export(pi_chord)
 export(pi_chord_type)
 export(pi_to_pc)
 export(pitch)
+export(play_pluck)
 export(represent)
 export(sample_rate)
+export(save_wav_pluck)
 export(sparse_fr_spectrum)
 export(sparse_pi_spectrum)
 export(sum_amplitudes)

NEWS.md

@@ -1,3 +1,7 @@
+# hrep 0.8.0
+
+- Added methods for synthesising audio.
+
 # hrep 0.7.0
 
 - Added wave representation.

R/play-pluck.R

@@ -0,0 +1,28 @@
+#' Play sound (pluck)
+#'
+#' Plays a sound with a plucked timbre.
+#'
+#' The sound is synthesised using \code{\link{save_wav_pluck}}
+#' and saved to a temporary file, which is then played from the R session.
+#'
+#' @note
+#' The command-line sound-processing program sox
+#' (\url{http://sox.sourceforge.net/})
+#' must be installed and available on the command line,
+#' making available the commands \code{sox} and \code{play}.
+#'
+#' @param x Object to play (see \code{\link{save_wav_pluck}} for valid options).
+#' @param ... Further parameters to pass to \code{\link{save_wav_pluck}}.
+#'
+#' @export
+play_pluck <- function(x, ...) {
+  UseMethod("play_pluck")
+}
+
+#' @export
+play_pluck.default <- function(x, ...) {
+  file <- tempfile(fileext = ".wav")
+  save_wav_pluck(x, file = file, ...)
+  system(paste0("play ", shQuote(file)))
+  file.remove(file)
+}

R/save-wav-pluck.R

@@ -0,0 +1,60 @@
+#' Save wav file (pluck)
+#'
+#' Saves object to a wav file using the 'pluck' timbre from sox
+#' (\url{http://sox.sourceforge.net/}).
+#'
+#' @note
+#' The command-line sound-processing program sox
+#' (\url{http://sox.sourceforge.net/})
+#' must be installed and available on the command line
+#' under the command \code{sox}.
+#'
+#' @param x Object to save; methods exist for individual chords
+#' and for vectors of chords (see \code{\link{vec}}).
+#' Chords are coerced to a \code{\link{pi_chord}} representation.
+#' @param file (Character scalar) Output file.
+#' @param chord_length (Numeric scalar) Length of each output chord, in seconds.
+#' @param ... Parameters passed to methods.
+#'
+#' @export
+save_wav_pluck <- function(x, file, chord_length = 1) {
+  UseMethod("save_wav_pluck")
+}
+
+#' @export
+save_wav_pluck.default <- function(x, ...) {
+  save_wav_pluck(pi_chord(x), ...)
+}
+
+#' @export
+save_wav_pluck.vec <- function(x, file, ...) {
+  files <- paste("chord-", seq_along(x), "-", sep = "") %>%
+    tempfile(fileext = ".wav")
+  for (i in seq_along(x)) save_wav_pluck(x[[i]], files[i], ...)
+  cmd <- c("sox", shQuote(files), shQuote(file)) %>% paste(collapse = " ")
+  system(cmd)
+  file.remove(files)
+}
+
+#' @export
+save_wav_pluck.coded_vec <- function(x, file, ...) {
+  save_wav_pluck(decode(x), file, ...)
+}
+
+#' @export
+save_wav_pluck.pi_chord <- function(x, ...) {
+  save_wav_pluck(fr_chord(x), ...)
+}
+
+#' @export
+save_wav_pluck.fr_chord <- function(x, file, chord_length = 1) {
+  checkmate::qassert(file, "S1")
+  checkmate::qassert(chord_length, "N1(0,)")
+  len <- sprintf("%.10f", as.numeric(chord_length))
+  freq <- sprintf("%.10f", as.numeric(x))
+  tones <- purrr::map_chr(freq,
+                          ~ sprintf('"|sox -n -p synth %s pluck %s"', len, .)) %>%
+    paste(collapse = " ")
+  cmd <- sprintf('sox --norm=-3 -m %s %s', tones, file)
+  system(cmd)
+}