audio synthesizer in unity?

hey I'm trying to make a organ that makes a kind of rainbow with colors when you play. by mapping 12 notes and 12 colors to 12 keys. so far i have the color working and an audioclip that plays, but i'd like it to keep playing the note if the key is held down. i could do this with a perfect loop of the note but then it loses all emotion kind of. i'd like the crescendo to stay and loop the audio clip somewhere in the middle so that I keep the fade in and out when the key is pressed or released. anyway of doing this?

this is my current code:

 using UnityEngine;
 using System.Collections;
 
 public class PUZZLE : MonoBehaviour {
     public KeyCode key1;
     public AudioClip note1;
     public Color defaultColor = Color.white;
     public Color newColor = Color.red;
     public float speed;
     
     void Start(){
         Mesh mesh = GetComponent<MeshFilter>().mesh;
         Color[] colors = new Color[mesh.vertices.Length];
         int i = 0;
         while (i < mesh.vertices.Length) {
             colors[i] = defaultColor;
             i++;
         }
         
         mesh.colors = colors;
     }
     void Update () {
         Mesh mesh = GetComponent<MeshFilter>().mesh;
         Color[] colors = mesh.colors;
         int i = 0;
         while (i < mesh.vertices.Length) {
             if(Input.GetKey(key1)){
                 audio.PlayOneShot(note1);
                 colors[i] = Color.Lerp(colors[i], newColor, speed * Time.deltaTime);
             } else {
                 colors[i] = Color.Lerp(colors[i], defaultColor, speed * Time.deltaTime);
             }
             i++;
         }
         mesh.colors = colors;
     }
 }