Chorale No 9 (Ermuntre dich mein schwacher Geist), Chorale No 14 (O Herre Gott, dein gottlich Wort), Chorale No 73 (Herr Jesu Christ, du höchstes Gut) and Chorale No 81 (Christus, der uns selig macht), are selected Lutheran chorales harmonized by Johann Sabastian Bach, an iconic composer of the Baroque era. In his harmonic processes, Bach explored various altered chords, harmonic devices, and non-harmonic tones. Focusing on a case study design, purposive sampling technique, and document analysis, the authors attempt to provide a formal analysis of the four selected harmonized chorales, employing parameters such as scale, vocal rages, melodic organization, harmony and tonality, non-chord tones, texture, and form. The analysis unravels his harmonic vocabulary to determine his compositional style. The harmonized chorales of Johann Sabastian Bach are therefore good educational materials of harmony and counterpoint andragogy for music students.