@discord-player/equalizer

import { EqualizerStream } from '@discord-player/equalizer';

// initialize 15 band equalizer stream
const equalizer = new EqualizerStream();

// set equalizer bands, in this case add some bass
equalizer.setEQ([
    { band: 0, gain: 0.25 },
    { band: 1, gain: 0.25 },
    { band: 2, gain: 0.25 }
]);

// input stream
const input = getPCMAudioSomehow();

// pipe input stream to equalizer
const output = input.pipe(equalizer);

// now do something with the output stream

import { BiquadStream, FilterType } from '@discord-player/equalizer';

// initialize biquad stream
const biquad = new BiquadStream();

// initialize with filter
const biquad = new BiquadStream({
    filter: FilterType.LowPass
});

// set filter
biquad.setFilter(FilterType.HighPass);

// set gain (Gain is only applicable to LowShelf, HighShelf and PeakingEQ)
biquad.setGain(5);

// input stream
const input = getPCMAudioSomehow();

// pipe input stream to biquad
const output = input.pipe(biquad);