Multiple gapless sound loops from one AudioSource (C#)

I have seen many questions about using multiple AudioSources but in my case, I want to use just one AudioSource, and one script controlling it. I have assigned 3 sound loops and I want to loop them without gaps all at once from one AudioSource, as well as stop and play individual sound loop with different individual volumes. Here's where I am right now:

 using UnityEngine;
 using System.Collections;
 
 [RequireComponent(typeof(AudioSource))]
 public class Sound : MonoBehaviour {
 
     AudioSource audioSource;
     public AudioClip audioClip1;
     public AudioClip audioClip2;
     public AudioClip audioClip3;
     [Range (0, 1)] public float audioClipVolume1;
     [Range (0, 1)] public float audioClipVolume2;
     [Range (0, 1)] public float audioClipVolume3;
 
     void Start () {
         audioSource = GetComponent<AudioSource> ();
         audioSource.loop = true;
     }
 
     void Update () {
         //How do I loop all 3 audio clips without gaps?
 
         //Tried using PlayOneShot
         //Checking if it is playing and playing it again creates gaps
 
         //Also, if one sound loop is shorter than the other soundloops, will wait untill
         //other sound loops finished to start playing again...
 
         if (!audioSource.isPlaying) {
             audioSource.PlayOneShot (audioClip1, audioClipVolume1);
             audioSource.PlayOneShot (audioClip2, audioClipVolume2);
             audioSource.PlayOneShot (audioClip3, audioClipVolume3);
         }
 
         //Tried changing clip
 
         //AudioSource can load only one clip, but allows for gapless looping
 
         audioSource.clip = audioClip2;
         audioSource.volume = audioClipVolume2;
         if (!audioSource.isPlaying) {
             audioSource.Play ();
         }
     }
 }