Unity - Adjust Volume with a Slider

public Slider musicSlider;
public Slider soundSlider;
public AudioMixer mixer;


private void Start()
{
    mixer.GetFloat("Music", out float bgmVolume);
    musicSlider.value = bgmVolume;
    mixer.GetFloat("Sound", out float soundVolume);
    soundSlider.value = soundVolume;
}


public void MusicMaster(float vol)
{
    vol = musicSlider.value;
    if (vol == -30f) vol = -80f;
    mixer.SetFloat("Music", vol);
}


public void SoundMaster(float vol)
{
    vol = soundSlider.value;
    if (vol == -30f) vol = -80f;
    mixer.SetFloat("Sound", vol);
}