gistfile1.txt

Observable.fromIterable(getAlbum())
    .flatMap(new Function<Album, ObservableSource<Song>>() {
        @Override
        public ObservableSource<Song> apply(Album album) throws Exception {
            return Observable.fromIterable(album.getSongs());
        }
    })
    .filter(new Predicate<Song>() {
        @Override
        public boolean test(@NonNull Song song) throws Exception {
            return false;
        }
    })
    .subscribeOn(Schedulers.newThread())
    .observeOn(AndroidSchedulers.mainThread())
    .subscribe(new Consumer<Song>() {
        @Override
        public void accept(Song song) throws Exception {
            System.out.println(song.getSongName());
        }
    });