Answer: Streaming services (older like radios, and modern like spotify) and Sintetizer
Explanation:
Older Streaming Services: Starting with radios, the producers needed to use pop songs in order to maintain the biggest possible audience, so pop creators are incentivized to make songs that enter in the radio standards.
Midi Sintetizer: You can listen to the 80s, 90s music and see how the presence of the synthesizer prevails, the "modern" sound that it had was very impactful in the time and the thousands of options that this instrument offered shaped in a great way the pop music that we know today.
Moder Streaming Services: This is a more modern example, a difference of the radio, here the listener can choose what to listen, so the artist has more freedom, none the less, streaming sites, like online sites, promotes more density of songs per album, which means that the songs need to be shorter than before.
