nowPlayingPlayground.swift

import Cocoa
import MediaPlayer

let bundle = CFBundleCreate(kCFAllocatorDefault, NSURL(fileURLWithPath: "/System/Library/PrivateFrameworks/MediaRemote.framework"))

let MRMediaRemoteRegisterForNowPlayingNotificationsPointer = CFBundleGetFunctionPointerForName(
    bundle, "MRMediaRemoteRegisterForNowPlayingNotifications" as CFString
)
typealias MRMediaRemoteRegisterForNowPlayingNotificationsFunction = @convention(c) (DispatchQueue) -> Void
let MRMediaRemoteRegisterForNowPlayingNotifications = unsafeBitCast(MRMediaRemoteRegisterForNowPlayingNotificationsPointer, to: MRMediaRemoteRegisterForNowPlayingNotificationsFunction.self)

let MRMediaRemoteGetNowPlayingInfoPointer = CFBundleGetFunctionPointerForName(
    bundle, "MRMediaRemoteGetNowPlayingInfo" as CFString)
typealias MRMediaRemoteGetNowPlayingInfoFunction = @convention(c) (DispatchQueue, @escaping ([String: Any]) -> Void) -> Void
let MRMediaRemoteGetNowPlayingInfo = unsafeBitCast(
    MRMediaRemoteGetNowPlayingInfoPointer, to: MRMediaRemoteGetNowPlayingInfoFunction.self
)

NotificationCenter.default.addObserver(forName: NSNotification.Name(rawValue: "kMRMediaRemoteNowPlayingInfoDidChangeNotification"), object: nil, queue: nil) { (notification) in
    MRMediaRemoteGetNowPlayingInfo(DispatchQueue.main, { (information) in
        debugPrint(information["kMRMediaRemoteNowPlayingInfoArtist"] as! String)
        debugPrint(information["kMRMediaRemoteNowPlayingInfoTitle"] as! String)
        debugPrint(information["kMRMediaRemoteNowPlayingInfoAlbum"] as! String)
    })
}
MRMediaRemoteRegisterForNowPlayingNotifications(DispatchQueue.main);