How to achieve Continuous ring twice in coroutine & OnGUI in C# ?

I’m a beginner . I’d like to achieve Continuous ring twice with two musical note 1 and 5 . It’s easy to be done by javascript, but not easy in C# . Those are my codes in C# below.I just heard one ring 1 . please tell me what’s wrong with it. Thank you in advance.

using UnityEngine;
using System.Collections;

public class Cchord : MonoBehaviour
{

    public AudioSource note1 ;
public AudioSource note5 ;



	

void OnGUI()
 {           
      
	      if(GUI.Button(new Rect(70,30,60,60),"Cchord"))
          {	
		              note1.Play(); 
			          DoWait() ;
		              note5.Play();
			          DoWait() ;
		              
			          return ;
		  }
		
		
	
	
 }



  IEnumerator DoWait()
{
  yield return new WaitForSeconds(1.0f);
}

}

In C#, coroutines need to be called with the function StartCoroutine. Here is what you should do :

public AudioSource note1 ;
public AudioSource note5 ;

void OnGUI()
{    
	if(GUI.Button(new Rect(70,30,60,60),"Cchord"))
	{    
		StartCoroutine( PlayMyMusic() );
	}
}

IEnumerator PlayMyMusic()
{
	note1.Play(); 
	yield return new WaitForSeconds(1.0f);
	note5.Play();
	yield return new WaitForSeconds(1.0f);
}