Short answers, pulled from the story.
Pop music emerged as a distinct entity in the mid-1950s from the United States and the United Kingdom. Before this period, the terms pop and rock were often synonymous, describing the same youth-oriented styles that swept the globe. The true definition of pop music crystallized only after the late 1960s when it was deliberately positioned as the commercial counterpart to rock music.
Multi-track recording emerged in the 1960s and allowed producers to create sounds that were impossible to replicate live. This technology shifted the focus from performance to production by using techniques like reverb, electronic sound effects, and orchestral arrangements to craft a polished commercial product. The genre relied heavily on the studio as an instrument during this period.
Phil Spector developed his signature Wall of Sound, a dense layered production technique that used multiple instruments playing the same parts to create a massive orchestral texture. His contemporaries such as Joe Meek utilized homemade electronic sound effects to create unique textures for acts like the Tornados. This era saw a departure from the refined Tin Pan Alley songwriting that had dominated earlier decades.
The song Blinding Lights by Canadian pop singer the Weeknd became the most-streamed song in the platform's history. It broke the record for the first track to hit 5 billion streams on the Spotify streaming platform. The song reached the top spot of Billboard's greatest Hot 100 songs of all time.
A 2018 study by researchers at the University of California Irvine concluded that pop music has become sadder since the 1980s. Elements of happiness and brightness were replaced by electronic beats that make the music sad yet danceable. This shift was evident in the 2010s when songs about escapism through partying became the most popular.