Dominant ninth chords had been employed by Beethoven, and eleventh chords appeared in Impressionist songs. Thirteenth chords appeared within the twentieth century. Usahakan belajar 1 lagu sampai bisa agar fokus saat berlatih tidak terpecah. Tidak perlu terburu-buru untuk menguasai lagu tertentu. Harmonies according to fourths and fifths also look in https://www.inschord.com/search/label/