Im using wavesurferjs library to handle my waveforms. https://wavesurfer.xyz/

What Im trying to do now is to stack a couple of waveforms on each other, or just simply render a couple of channels in one audio (in one waveform instance). I found in the docs info about splitting channels, but I wonder if this is what im looking for. I need to be able to change volume of only e.g. Vocals or Bass. Please take a look at attached gif. This is what Im trying to achieve.

What I tried is to use that split channel, but the waveform is not appearing and I guess Im not able to change volume of each channel because there’s no way to get to the each channel separately.

const ws = WaveSurfer.create({
    backend: 'MediaElement',
    container: '#container',
    splitChannels: [
      {
        peaks: [//peaks here],
        container: '#container',
        waveColor: 'yellow',
        progressColor: 'lightyellow',
        backend: 'MediaElement',
        url: 'url_to_the_bass_file',
      },
      {
        peaks: [//peaks here],
        container: '#container',
        waveColor: 'blue',
        progressColor: 'lightblue',
        backend: 'MediaElement',
        url: 'url_to_the_vocals_file',
      },
    ],
  })

// how to set volume of each channel? is it even possible?

Looking forward for any help or hint.

The example on gif comes from https://www.bandlab.com/splitter