Multivoice Chorus
This is an implementation of a Multivoice (as opposed to Multiscale) chorus algorithm. Its uses a novel, sinc based noise interpolation method to produce a subtle modulation law which makes it possible to get away with larger numbers of voices without the metallic, artificial sound common in chorus effects.
delay_tbl);
free(plugin_data->prev_peak_pos);
free(plugin_data->next_peak_pos);
free(plugin_data->prev_peak_amp);
free(plugin_data->next_peak_amp);
free(plugin_data->dp_targ);
free(plugin_data->dp_curr);
]]>
0) {
law_separation = law_p / laws;
} else {
law_separation = 0;
}
// Calculate voice spread in samples
base_offset = (f_clamp(voice_spread, 0.0f, 2.0f) * sample_rate) / 1000;
// Calculate base delay size in samples
d_base = (f_clamp(delay_base, 5.0f, 40.0f) * sample_rate) / 1000;
// Calculate delay depth in samples
delay_depth = f_clamp((law_p * f_clamp(detune, 0.0f, 10.0f)) / (100.0f * M_PI), 0.0f, delay_size - d_base - 1 - (base_offset * laws));
// Calculate output attenuation
atten = DB_CO(f_clamp(attendb, -100.0, 24.0));
for (pos = 0; pos < sample_count; pos++) {
// N times per law 'frequency' splurge a new set of windowed data
// into one of the N law buffers. Keeps the laws out of phase.
if (laws > 0 && (count % law_separation) == 0) {
next_peak_amp[law_roll] = (float)rand() / (float)RAND_MAX;
next_peak_pos[law_roll] = count + law_p;
}
if (laws > 0 && (count % law_separation) == law_separation/2) {
prev_peak_amp[law_roll] = (float)rand() / (float)RAND_MAX;
prev_peak_pos[law_roll] = count + law_p;
// Pick the next law to be changed
law_roll = (law_roll + 1) % laws;
}
out = input[pos];
if (count % 16 < laws) {
unsigned int t = count % 16;
// Calculate sinus phases
float n_ph = (float)(law_p - abs(next_peak_pos[t] - count))/law_p;
float p_ph = n_ph + 0.5f;
if (p_ph > 1.0f) {
p_ph -= 1.0f;
}
dp_targ[t] = f_sin_sq(3.1415926f*p_ph)*prev_peak_amp[t] + f_sin_sq(3.1415926f*n_ph)*next_peak_amp[t];
}
for (t=0; tcount = count;
plugin_data->law_pos = law_pos;
plugin_data->last_law_p = last_law_p;
plugin_data->law_roll = law_roll;
plugin_data->delay_pos = delay_pos;
]]>
Number of voices
Delay base (ms)
Voice separation (ms)
The individual voices can either be running at the same base delay (set this to zero) or staggered.
Setting this to non-zero values can make the output sound richer, but will make it sound grainy with some type of signal.
Detune (%)
The maximum amount that a voice will be detuned by. I recommend a value of 1, but you may be able to get away with higher values if the signal is less harmonic.
LFO frequency (Hz)
The frequency that the detune effect will be modulated at. A matter of taste, for most types of input lower will be more subtle.
Output attenuation (dB)
With large numbers of voices the output can become too high, so use this to trim the amplitude to a more helpful level.
Input
Output