Using multiple AudioClips with data created using SetData causes distortion

I am trying to create a music generation app (the user writes a short score and the app then plays the corresponding notes), where each separate note is handled as a separate AudioSource with its AudioClip created dynamically by setting the clip's data according to a sine wave function using AudioClip.SetData.

For individual notes or two notes together this works fine, but if I have three or more notes playing at the same I get severe distortion.

In case the function that sets the data is taking too much processing power I tested it with all the data pre-set, but the problem still occurs so I presume it is something else.

I also tried playing three music mp3 files instead of my dynamically-generated notes - this worked fine with no distortion.

Any suggestions what I may be doing wrong or what I should look out for?

 using UnityEngine;
 using System.Collections;
 
 public class KeyScript : MonoBehaviour {
 
     public float Duration = 1;
     public int KeyPitch = 48;
 
     public Note Note;
     private int sampleRate;
     private AudioSource source;
 
     // Use this for initialization
     void Start () {
         sampleRate = AudioSettings.outputSampleRate;
         source = GetComponent<AudioSource>();
     }
     
     // Update is called once per frame
     void Update () {
     
     }
 
     void OnMouseDown () {
         Note = new Note(Scale.pitches[KeyPitch], Duration, sampleRate, source);
         Note.Play ();
     }
 }
 
 public class Note
 {
     private Pitch pitch;
     private float length;
     private int sampleRate;
     private AudioClip clip;
     private AudioSource source;
 
     public Note(Pitch Pitch, float Length, int SampleRate, AudioSource Source)
     {
         this.pitch = Pitch;
         this.length = Length;
         this.sampleRate = SampleRate;
         this.source = Source;
         this.clip = AudioClip.Create ("Procedural Tone", (int)(sampleRate * length), 1, sampleRate, false);
 
         int count = 0;
         float[] data = new float[(int)(sampleRate * length)];
         while (count < data.Length)
             {
             data[count] = Mathf.Sign(Mathf.Sin(2 * Mathf.PI * pitch.Frequency * count / sampleRate));
             count++;
             }
 
         clip.SetData (data, 0);
         source.clip = clip;
     }
 
     public void Play()
     {
         source.Play ();
     }
 }
 
 public class Pitch
 {
     private string name;
     private float frequency;
     
     public float Frequency
     {
         get { return frequency;}
     }
     
     public Pitch(string Name, float Frequency)
     {
         this.name = Name;
         this.frequency = Frequency;
     }
     
     public override string ToString()
     {
         return name;
     }
 }
 
 public static class Scale
 {
     public static Pitch[] pitches =
     {
         new Pitch("C0", 16.35f),
         new Pitch("C#0/Db0", 17.32f),
         new Pitch("D0", 18.35f),
         new Pitch("D#0/Eb0", 19.45f),
         new Pitch("E0", 20.6f),
         new Pitch("F0", 21.83f),
         new Pitch("F#0/Gb0", 23.12f),
         new Pitch("G0", 24.5f),
         new Pitch("G#0/Ab0", 25.96f),
         new Pitch("A0", 27.5f),
         new Pitch("A#0/Bb0", 29.14f),
         new Pitch("B0", 30.87f),
         new Pitch("C1", 32.7f),
         new Pitch("C#1/Db1", 34.65f),
         new Pitch("D1", 36.71f),
         new Pitch("D#1/Eb1", 38.89f),
         new Pitch("E1", 41.2f),
         new Pitch("F1", 43.65f),
         new Pitch("F#1/Gb1", 46.25f),
         new Pitch("G1", 49f),
         new Pitch("G#1/Ab1", 51.91f),
         new Pitch("A1", 55f),
         new Pitch("A#1/Bb1", 58.27f),
         new Pitch("B1", 61.74f),
         new Pitch("C2", 65.41f),
         new Pitch("C#2/Db2", 69.3f),
         new Pitch("D2", 73.42f),
         new Pitch("D#2/Eb2", 77.78f),
         new Pitch("E2", 82.41f),
         new Pitch("F2", 87.31f),
         new Pitch("F#2/Gb2", 92.5f),
         new Pitch("G2", 98f),
         new Pitch("G#2/Ab2", 103.83f),
         new Pitch("A2", 110f),
         new Pitch("A#2/Bb2", 116.54f),
         new Pitch("B2", 123.47f),
         new Pitch("C3", 130.81f),
         new Pitch("C#3/Db3", 138.59f),
         new Pitch("D3", 146.83f),
         new Pitch("D#3/Eb3", 155.56f),
         new Pitch("E3", 164.81f),
         new Pitch("F3", 174.61f),
         new Pitch("F#3/Gb3", 185f),
         new Pitch("G3", 196f),
         new Pitch("G#3/Ab3", 207.65f),
         new Pitch("A3", 220f),
         new Pitch("A#3/Bb3", 233.08f),
         new Pitch("B3", 246.94f),
         new Pitch("C4", 261.63f),
         new Pitch("C#4/Db4", 277.18f),
         new Pitch("D4", 293.66f),
         new Pitch("D#4/Eb4", 311.13f),
         new Pitch("E4", 329.63f),
         new Pitch("F4", 349.23f),
         new Pitch("F#4/Gb4", 369.99f),
         new Pitch("G4", 392f),
         new Pitch("G#4/Ab4", 415.3f),
         new Pitch("A4", 440f),
         new Pitch("A#4/Bb4", 466.16f),
         new Pitch("B4", 493.88f),
         new Pitch("C5", 523.25f),
         new Pitch("C#5/Db5", 554.37f),
         new Pitch("D5", 587.33f),
         new Pitch("D#5/Eb5", 622.25f),
         new Pitch("E5", 659.25f),
         new Pitch("F5", 698.46f),
         new Pitch("F#5/Gb5", 739.99f),
         new Pitch("G5", 783.99f),
         new Pitch("G#5/Ab5", 830.61f),
         new Pitch("A5", 880f),
         new Pitch("A#5/Bb5", 932.33f),
         new Pitch("B5", 987.77f),
         new Pitch("C6", 1046.5f),
         new Pitch("C#6/Db6", 1108.73f),
         new Pitch("D6", 1174.66f),
         new Pitch("D#6/Eb6", 1244.51f),
         new Pitch("E6", 1318.51f),
         new Pitch("F6", 1396.91f),
         new Pitch("F#6/Gb6", 1479.98f),
         new Pitch("G6", 1567.98f),
         new Pitch("G#6/Ab6", 1661.22f),
         new Pitch("A6", 1760f),
         new Pitch("A#6/Bb6", 1864.66f),
         new Pitch("B6", 1975.53f),
         new Pitch("C7", 2093f),
         new Pitch("C#7/Db7", 2217.46f),
         new Pitch("D7", 2349.32f),
         new Pitch("D#7/Eb7", 2489.02f),
         new Pitch("E7", 2637.02f),
         new Pitch("F7", 2793.83f),
         new Pitch("F#7/Gb7", 2959.96f),
         new Pitch("G7", 3135.96f),
         new Pitch("G#7/Ab7", 3322.44f),
         new Pitch("A7", 3520f),
         new Pitch("A#7/Bb7", 3729.31f),
         new Pitch("B7", 3951.07f),
         new Pitch("C8", 4186.01f),
         new Pitch("C#8/Db8", 4434.92f),
         new Pitch("D8", 4698.63f),
         new Pitch("D#8/Eb8", 4978.03f),
         new Pitch("E8", 5274.04f),
         new Pitch("F8", 5587.65f),
         new Pitch("F#8/Gb8", 5919.91f),
         new Pitch("G8", 6271.93f),
         new Pitch("G#8/Ab8", 6644.88f),
         new Pitch("A8", 7040f),
         new Pitch("A#8/Bb8", 7458.62f),
         new Pitch("B8", 7902.13f)
     };
 }