MissingComponentException: no AudioClip even if i add it

so i was trying to use the beat detector by allanpichardo:

https://github.com/allanpichardo/Unity-Beat-Detection

I wanted to understand what the program was doing, so i didnt simply copy-paste everything. I typed everything myself, and came across something with an audio Object. The following lines will show you what he wrote and what i had to write instead ( i guess ):

 AudioProcessor, line 81:
 Him: samplingRate = audio.clip.frequency;
 Me:   samplingRate = GetComponent<AudioClip>().frequency;

 AudioProcessor, line 122:
 Him: if (audio.isPlaying) ...
 Me:   if (GetComponent<AudioSource>().isPlaying) ...

 AudioProcessor, line 125:
 ​​​​​​​​​​Him: audio.GetSpectrumData(spectrum, 0, FFTWindow.BlackmanHarris);
 Me:  GetComponent<AudioSource>().GetSpectrumData(spectrum, 0, FFTWindow.BlackmanHarris);

I thought this must be the new way to write it ( had the same problem with a tutorial on the internet few weeks ago with "rigidbody", untill i read you have to use GetComponent() now ). It makes sense to me. So i added a AudioSource to my Main Camera, draged and droped my audiofile into the "AudioClip"-field and added the "Example"-script to an Object.

Running the program throws 2 different Exceptions. Iam going to focus in the first one. The second one is probably caused by the first one, so iam not taking this any further.

MissingComponentException: There is no 'AudioClip' attached to the "Main Camera" game object, but a script is trying to access it.

Why cant the program find my AudioClip and how do i fix this issue?

Thanks for the effort,

replayleif