How to access all winmm.dll classes and properties?

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C#

I successfully integrated the [volume level] code in my program. Yay for me. I find it on internet. I'm not that smart yet. But I want to be... maybe with your help.

[DllImport("winmm.dll")]
public static extern int waveOutGetVolume(IntPtr hwo, out uint dwVolume);
[DllImport("winmm.dll")]
public static extern int waveOutSetVolume(IntPtr hwo, uint dwVolume);
double volume = 100;
void Volume()
{
    double NewVolume = ((ushort.MaxValue / 100) * volume);
    waveOutSetVolume(IntPtr.Zero, (uint)NewVolume);
}

Now I am curious [How to see] all the classes and [some samples using and calling] those classes from this winmm.dll.
I imagine there is somewhere a list with all the properties and classes from that dll on the internet.
Is it?
Thank you very much !

What I have tried:

the code is in description. ^