R/freq2wave.R

In egenn/music: Learn and Experiment with Music Theory

# freq2wave.R
# ::music::
# 2019 E.D. Gennatas lambdamd.org

#' Frequency to waveform
#'
#' @inheritParams playFreq
#' @param frequency Float, vector: Frequency/ies to convert to waveform
#' @param plot Logical: If TRUE, plot wave(s) using \link{mplot}
#'
#' @author E.D. Gennatas
#' @export
#' @examples
#' wave <- freq2wave(note2freq(buildChord("A4", "sus2")))

freq2wave <- function(frequency,
                      oscillator = c("sine", "square", "saw", "triangle"),
                      duration = 1,
                      BPM = 120,
                      sample.rate = 44100,
                      attack.time = 50,
                      inner.release.time = 50,
                      plot = FALSE) {
    oscillator <- match.arg(oscillator)
    .t <- seq(0, duration / BPM * 60, 1 / sample.rate)
    n.freqs <- length(frequency)

    # Wave ====
    wave <- sapply(seq(n.freqs), function(i) {
        switch(oscillator,
            sine = sin(.t * frequency[i] * 2 * pi),
            square = sign(sin(.t * frequency[i] * 2 * pi)),
            saw = 2 * (.t * frequency[i] - floor(.5 + .t * frequency[i])),
            triangle = 2 * abs(2 * (.t * frequency[i] - floor(.5 + .t * frequency[i]))) - 1
        )
    })

    n.samples <- NROW(wave)

    # Attack ====
    if (attack.time > 0) {
        attack <- rep(1, n.samples)
        # If attack.time was inappropriately long for your waveform, you may have longer attack than wave
        n.attack.samples <- round(min(n.samples, attack.time / 1000 * sample.rate))
        attack[seq(n.attack.samples)] <- seq(0, 1, length.out = n.attack.samples)
        wave <- wave * attack
    }

    # Inner Release ====
    if (inner.release.time > 0) {
        inner.release <- rep(1, n.samples)
        n.inner.release.samples <- round(min(n.samples, inner.release.time / 1000 * sample.rate))
        inner.release[n.samples - (seq(n.inner.release.samples) - 1)] <- seq(0, 1, length.out = n.inner.release.samples)
        wave <- wave * inner.release
    }

    .names <- if (!is.null(names(frequency))) names(frequency) else paste(frequency, "Hz")
    colnames(wave) <- .names
    if (plot) mplot(wave)
    wave
} # music::freq2wave