using System;
using System.Reflection;
using UnityEditor;
using UnityEngine;

public class Example
{
    [InitializeOnLoadMethod]
    private static void Hoge()
    {
        // AudioClip は用意する必要がある
        var clip = AssetDatabase.LoadAssetAtPath<AudioClip>( "Assets/TypeWriter Sound Effects/Key 1.wav" );

        var isDown = false;
        EditorApplication.CallbackFunction function = () =>
        {
            var e = Event.current;
            if ( !isDown && e.type == EventType.KeyDown )
            {
                isDown = true;
                PreviewAutioClip( clip );
            }
            if ( isDown && e.type == EventType.KeyUp )
            {
                isDown = false;
            }
        };
        var bindingAttr = BindingFlags.Static | BindingFlags.Instance | BindingFlags.NonPublic;
        var info = typeof( EditorApplication ).GetField( "globalEventHandler", bindingAttr );
        var functions = info.GetValue( null ) as EditorApplication.CallbackFunction;
        functions += function;
        info.SetValue( null, functions );
    }

    private static void PreviewAutioClip( AudioClip clip )
    {
        var unityEditorAssembly = typeof( AudioImporter ).Assembly;
        var audioUtilClass = unityEditorAssembly.GetType( "UnityEditor.AudioUtil" );

        var method = audioUtilClass.GetMethod
        (
            "PlayClip",
            BindingFlags.Static | BindingFlags.Public,
            null,
            new Type[] { typeof(AudioClip) },
            null
        );

        method.Invoke( null, new object[] { clip } );
    }
}