Synchronize Folders with iTunes Playlists. Usage: sync.exe [parent-folder] [parent-playlist]. Defaults to your OneDrive/Music Folder.

iTunes Sync.cs

//reference iTunesLib from COM
using iTunesLib;
using Microsoft.Win32;
using System;
using System.IO;
using System.Threading;
using System.Linq;

class Program
{
    readonly static string[] Extensions = new[] { ".mp3", ".m4a", ".aac", ".aiff", ".wav", ".aa", "m4p" };

    [STAThread]

    static void Main(string[] args)

    {
        var iTunesApp = new iTunesAppClass();

        var folder = args.Any() ? Path.GetFullPath(args[0]) : Path.Combine(Registry.GetValue("HKEY_CURRENT_USER\\Software\\Microsoft\\SkyDrive", "UserFolder",
            Registry.GetValue("HKEY_CURRENT_USER\\Software\\Microsoft\\Windows\\CurrentVersion\\SkyDrive", "UserFolder", null)).ToString(), @"Music\");
        var parent = args.Length > 1 ? args[1] : null;


        var dir = new DirectoryInfo(folder);

        var playlists = iTunesApp.LibrarySource.Playlists.Cast<IITPlaylist>().ToArray();

        foreach (var pair in dir.GetDirectories().Select(x => new
        {
            dir = x,
            playlist = playlists.SingleOrDefault(y => y.Name == x.Name && (((dynamic)y).Parent.Name == parent || parent == null))
        }))
        {
            if (pair.playlist == null)
                continue;
            var tracks = pair.playlist.Tracks.Cast<IITTrack>().Select(track => new { track, location = (string)((dynamic)track).Location }).ToArray();


            foreach (var file in pair.dir.GetFiles().Where(x => Extensions.Contains(x.Extension)))
            {
                try
                {
                    var tagFile = TagLib.File.Create(file.FullName);
                    if (!tracks.Any(x => x.location == file.FullName || x.track.Name == tagFile.Tag.Title))
                    {
                        dynamic playlist = (dynamic)pair.playlist;
                        var status = playlist.AddFile(file.FullName);
                        while (status.InProgress) { Thread.Sleep(100); }
                        Console.WriteLine(status.Tracks[1].Name + " added");
                    }
                }
                catch (Exception e)
                {
                    Console.WriteLine("Error: " + e.Message);
                }
            }
        }

        Console.WriteLine("finished");
        Console.ReadKey();

    }

}