Unity C# Keyboard keys to pitch of a sound conversion

PitchShift.cs

///
/// Changes pitch of any audio clip to match a pressed key on a (piano) keyboard
/// if a sound is in C4 (440hz) then it will perfectly match the scale
/// by Nothke
/// 
/// QWERTY.. row for white keys
/// 12345... row for black keys
/// press C to toggle chord mode in game
/// press N or M for minor or major
/// press A to toggle arpeggiate
/// 
/// Licence: CC0
///

using UnityEngine;
using System.Collections;

public class PitchShift : MonoBehaviour
{
    [Tooltip("Add a sound clip of a single tone in C4 (at 440Hz)")]
    public AudioClip clip;

    [Tooltip("Will play a chord (4 tones) of the key pressed")]
    public bool playChord;
    public enum Chord { Major, Minor };
    [Tooltip("Chose which chord to play")]
    public Chord chord;
    [Tooltip("Plays a chord in ascending sequence")]
    public bool arpeggiate;
    [Tooltip("Time between tones when arpeggiating")]
    public float arpeggioTime = 0.1f;

    public float KeyToPitch(int midiKey)
    {
        int c4Key = midiKey - 72;

        float pitch = Mathf.Pow(2, c4Key / 12f);

        return pitch;
    }

    void Play(int midiKey)
    {
        if (playChord)
        {
            PlayChord(midiKey);
            return;
        }

        PlayNote(midiKey, 1);
    }

    void PlayChord(int midiKey)
    {
        if (arpeggiate)
        {
            StartCoroutine(Arpeggio(midiKey));
            return;
        }

        PlayNote(midiKey, 0.25f);

        if (chord == Chord.Major)
        {
            PlayNote(midiKey + 4, 0.25f);

        }
        else if (chord == Chord.Minor)
        {
            PlayNote(midiKey + 3, 0.25f);
        }

        PlayNote(midiKey + 7, 0.25f);
        PlayNote(midiKey + 12, 0.25f);
    }

    IEnumerator Arpeggio(int midiKey)
    {
        PlayNote(midiKey, 0.8f);
        yield return new WaitForSeconds(arpeggioTime);

        if (chord == Chord.Major)
        {
            PlayNote(midiKey + 4, 0.8f);
            yield return new WaitForSeconds(arpeggioTime);

        }
        else if (chord == Chord.Minor)
        {
            PlayNote(midiKey + 3, 0.8f);
            yield return new WaitForSeconds(arpeggioTime);
        }

        PlayNote(midiKey + 7, 0.8f);
        yield return new WaitForSeconds(arpeggioTime);

        PlayNote(midiKey + 12, 0.8f);
        yield return new WaitForSeconds(arpeggioTime);
    }

    void PlayNote(int midiKey, float volume)
    {
        AudioSource source = gameObject.AddComponent<AudioSource>();

        source.clip = clip;
        source.panLevel = 0;
        source.volume = volume;
        source.pitch = KeyToPitch(midiKey);
        source.Play();

        Destroy(source, source.clip.length);
    }

    void Update()
    {
        if (Input.GetKeyDown("m"))
            chord = Chord.Major;

        if (Input.GetKeyDown("n"))
            chord = Chord.Minor;

        if (Input.GetKeyDown("c"))
            playChord = !playChord;

        if (Input.GetKeyDown("a"))
            arpeggiate = !arpeggiate;

        // Keyboard keys > QUERTY.. row for white keys, and 12345.. row for black keys

        if (Input.GetKeyDown("q"))
            Play(72);

        if (Input.GetKeyDown("2"))
            Play(73);

        if (Input.GetKeyDown("w"))
            Play(74);

        if (Input.GetKeyDown("3"))
            Play(75);

        if (Input.GetKeyDown("e"))
            Play(76);

        if (Input.GetKeyDown("r"))
            Play(77);

        if (Input.GetKeyDown("5"))
            Play(78);

        if (Input.GetKeyDown("t"))
            Play(79);

        if (Input.GetKeyDown("6"))
            Play(80);

        if (Input.GetKeyDown("y"))
            Play(81);

        if (Input.GetKeyDown("7"))
            Play(82);

        if (Input.GetKeyDown("u"))
            Play(83);

        if (Input.GetKeyDown("i"))
            Play(84);

        if (Input.GetKeyDown("9"))
            Play(85);

        if (Input.GetKeyDown("o"))
            Play(86);

        if (Input.GetKeyDown("0"))
            Play(87);

        if (Input.GetKeyDown("p"))
            Play(88);
    }
}