PianoKey.cs

using UnityEngine;
using System.Collections;
using UnityEngine.Rendering;

/// <summary>
/// This is meant to be placed on a child GameObject with a collider.
/// </summary>
public class PianoKey : MonoBehaviour {

    static double RootThing = YRoot(12, 2);
    public static double Volume = .8f;

    public const double Frequency = 440;
    public const double SamplingFrequency = 48000;

    public KeySet keySet;

    public int keyNumber;
    public int KeyNumber {
        get { return keySet.GetKeyNumber(keyNumber); }
    }

    double keyFrequency;

    bool hit;
    bool onDown;
    bool onUp;

    float time = 1;
    float keyAnimationTime;

    double phase;

    AudioSource Audio { get; set; }

    void Awake() {
        Audio = GetComponent<AudioSource>();
        keySet = GetComponentInParent<KeySet>();

        keyFrequency = GetKeyFrequency(KeyNumber);
    }

    void Update() {
        if(onDown) {
            time = 1.05f;

            if(!Audio.isPlaying)
                Audio.Play();

            if(keyAnimationTime < 1)
                keyAnimationTime = Mathf.Min(keyAnimationTime + Time.deltaTime * 8, 1);
        }
        else {
            if(keyAnimationTime > 0)
                keyAnimationTime = Mathf.Max(keyAnimationTime - Time.deltaTime * 2, 0);
        }

        float animationTime = -Mathf.Clamp01(keyAnimationTime);

        Vector3 position = transform.parent.localPosition;
        position.y = animationTime * .3f;
        transform.parent.localPosition = position;

        Vector3 rotation = transform.parent.localEulerAngles;
        rotation.x = animationTime * 8;
        transform.parent.localEulerAngles = rotation;
    }

    void LateUpdate() {
        onDown = false;
        onUp = false;

        if(Audio.isPlaying) {
            if(time > 0) {
                time -= Time.deltaTime * Mathf.Max(time, time > .5f ? 2 : .25f);

                if(time < 0) {
                    time = 0;
                    phase = 0;

                    Audio.Stop();
                }
            }
        }
        else if(time < 1) {
            time = Mathf.Min(time + Time.deltaTime * 4, 1);
        }
    }

    void OnAudioFilterRead(float[] data, int channels) {
        if(time > 0) {
            double increment = System.Math.Pow(2, KeyNumber / 12d) * Frequency * 2 * Mathf.PI / SamplingFrequency;

            for(int i = 0; i < data.Length; i += channels) {
                phase += increment;
                data[i] = (float)(System.Math.Sin(phase) * Volume * Mathf.Clamp01(time));

                if(channels == 2) data[i + 1] = data[i];
                if(phase > 2 * Mathf.PI) phase = 0;
            }
        }
    }

    static double GetKeyFrequency(int keyNumber) {
        return System.Math.Pow(2, keyNumber / 12d) * Frequency;
    }

    static double YRoot(double value, int power) {
        return System.Math.Pow(value, 1d / power);
    }

    /// <summary>
    /// Don't know if this gives the right result yet. Check the keyFrequency variable in the inspector (debug mode) after hitting play.
    /// </summary>
    /// <param name="keyFrequency"></param>
    /// <returns></returns>
    static double GetKey(double keyFrequency) {
        return (System.Math.Log(12, 2) * (keyFrequency / Frequency)) + 49;
    }

    void OnMouseDown() {
        //hit = true;
        //onDown = true;
    }

    void OnMouseOver() {
        if(Input.GetMouseButton(0)) {
            //if(onDown != true) {
            //  keyAnimationTime = 0;
            //}

            onDown = true;
        }
    }

    void OnMouseUp() {
        //hit = false;
        //onUp = true;
    }

}