filtered_delay.gdsp

# Filtered feedback delay: delay line with a lowpass filter in the
# feedback path and interpolated reads. Uses history for single-sample
# feedback. Demonstrates delay_read with interp=linear and the history
# feedback pattern.

graph filtered_delay (sr=48000) {
    in input
    out output = wet_mix

    param time     1..2000  = 500     # delay time in ms
    param feedback 0..0.99  = 0.6
    param tone     0..1     = 0.3     # lowpass on feedback
    param mix      0..1     = 0.5

    delay dly 96000

    # Convert ms to samples
    time_samps = mstosamps(time)

    # Read from delay line with interpolation
    tap = delay_read dly (time_samps, interp=linear)

    # Filter the feedback
    fb_filtered = onepole(tap, tone)

    # Write input + filtered feedback into delay
    delay_write dly (input + fb_filtered * feedback)

    # Crossfade dry/wet
    dry     = input * (1 - mix)
    wet     = tap * mix
    wet_mix = dry + wet
}