“7 Wonders” is vague and to remove subjectivity, requires definition. I will give you some compositions that from my perspective are wonders because at the time of publication and first performance they changed the director classical music. I am not formally educated but self educated on musical history and structure to give me a greater appreciation of musical as an audiophile.
- Ancient Music: von Bingin Ordo Virtutum - chant to drama
- Romantic: Tallis Spem in Alium - 40 part motet that was first to develop massed sound pressure in a hall.
- Baroque: Bach Well Tempered Clavier - stressing a structural foundation for music and unrestrained modulation.
- Classical: Mozart Symphony No. 40 - moved classical from the light to dark side of emotional drama.
- Early Romantic: Beethoven Symphony No. 3 - using composition for personal and philosophical expression, intense emotional shifts.
- Late Romantic: Wagner Tristan and Isolde - Known for the opening chord - the Tristan chord - moved music structure from resolved melodic structures in traditional thirds, fifths to a more dissonant resolved seventh, setting structure for 20th century composers.
- Late Romantic: Mahler Symphony No.9 - the piece the started the end of Romantic structure bringing contrapuntal chaos and dark emotion, with an unresolved structure at the end. Music moved into the 20th century.
- 20th Century: Stravinsky Right of Spring - the end of romantic rules of structure, harmony, and rhythm … dissonance and unrestricted polyrhythms.
- Modern: Reich Music for 18 Musicians - minimalism