How did harmony affect melodies in Western music after the Renaissance?

Following the Renaissance, the evolution of the common practice system profoundly altered the inner logic of melodies in Western music. As harmony became a structured, foundational element, melodies began to function as the "surface" of underlying harmonic patterns.1

Key developments in this relationship include:

• Harmonic Implication: Because the ear perceives harmonic patterns even in successive notes, melodies began to carry strong implications of chords. Composers utilized scale passages and arpeggiated chords to clearly outline keys and harmonic directions, even in unaccompanied works like those by J.S. Bach.1
• Polarization of Lines: With the rise of basso continuo and homophony in the 17th century, a clear distinction emerged between the expressive melodic line and the bass line, which served as the generating force for harmonies.2
• Melodic Independence: While melodies were often bearers of their own harmonic implications, composers seeking greater expressiveness—particularly in the Romantic era—often introduced long dissonances to create a sense of melodic independence from the harmonic underpinning.1
• Reversal in the 20th Century: In some modern techniques, such as Schoenberg's 12-tone system, the traditional relationship was reversed, with harmony becoming the result of melodic sequences.1