Every once in a while  I have two songs simultaneously go through my head where I reflect on the similarities. It is common for people to lament that songs sound so much more similar today than they used to, but the truth is that there has often been a strong similarity in the way that music sounds within generations, for a variety of reasons. Whether the same songs were covered by many musicians competing for chart dominance, or whether prolific songwriters on the order of Carole King or Cole Porter simply happened to write large amounts of songs that other people sang, or that they themselves sang, the music industry has always faced the problem of soundalike material. Even those of us who play classical music often will find ourselves trying to differentiate Mozart symphonies, which can sound fairly similar once one has played a few of them. If classical musicians at the peak of high art can wonder about the similarities of one piece of music to another, then surely those of us who are paying attention to music of a more commercial nature can wonder about the same without limiting that tendency to only one era of music, like our own.
For example, recently the song “Who’s Zoomin Who?” came into my head. Admittedly, this is not a song I tend to think about often; it was a popular song in 1985, a top 10 hit for Aretha Franklin from her album of the same name, but while I thought of it I happened to think of a separate song that had the same sort of chord progression, “How Will I Know” by Whitney Houston. Both of the song titles feature queries with the same number of syllables, making the songs even more similar than most where such striking parallels can be found. In an example like this, one needs to know some details to determine why the songs are similar, especially where, as in this case, there is no known lawsuit between the parties that argued that the song was stolen by one of the parties. “Who’s Zooming Who?” was released as a single in August 1985 and was co-written by Arethra Franklin, Preston Glass, and Narada Michael Walden (who also produced the track) . In contrast, “How Will I Know” was released as a single in November 1985 (although the album it was on had been released in February of that year), and was written by George Merrill, Shannon Rubicam, and Narada Michael Walden, who also produced the song .
In this case, the source of the similarity is extremely straightforward. All hands point to Narada Michael Walden, who co-wrote and produced both songs. Although some reviewers  noted the similarity between “How Will I Know” and songs like the Pointer Sisters’ “He’s So Shy,” but the similarities between the songs by Aretha and Whitney appear to have escaped wide scrutiny, possibly due to the fact that while “How Will I Know” is an enduring 80’s standard, “Who’s Zoomin’ Who?” has been largely forgotten, the song lacking a music video to keep it in the public eye. Of interest is the fact that Aretha appeared in the Whitney Houston video and that both artists were on the same label. Since we know far more about the story of “How Will I Know,” and that Narada Michael Walden was not the original writer of the song, but that the song had been provided to him by its original songwriters who were extremely intent that Whitney Houston sing their song while he was working on Aretha Franklin’s album. It seems very likely that recognizing a particular hook in the song that Whitney Houston was recording led Naruda to give the same hook to a song by Aretha Franklin, since the hook is a good one. As a result two hit songs sprang from the same sort of hook in the chorus, and the producer got co-writing credit on both of the songs for providing his hit-making touch, and no lawsuits were involved.
Not everyone is so lucky. It is easy to slight the contribution of producers, but their duty is to craft a song that comes alive and that buries itself like an earworm so that it sticks in the thoughts of the listener, leading to more requests and purchases. There is a delicate art in knowing what is capturing the attention of the audience and presenting the musicians in their best light. Having a keen ear for hooks helps a producer craft good hits, and that keeps a producer coming back for career minded musicians and profit-oriented labels. When a producer is wise, he manages to make himself a co-writer of the songs that he produces, which means that the similarities between songs fall into the realm of self-plagiarism where a writer copies himself, as we are all known to do from time to time, especially when we are immensely prolific and fluent. When a producer is unwise, an earworm from someone else’s song ends up lodged in his head and he spreads the same hook to songs he has written, and then passes it off as an original hook, only to lead to problems when the song’s samples are being cleared or when the song is released to general praise, and the threat of legal action from those whose songwriting was appropriated without recognition and payment. No one likes that, yet in some cases lawsuits are avoided because the producer is able to embed himself (usually) early enough in the process to ensure that he has a stake in all of the songs that contain that particular hook that are being released simultaneously, the presence of multiple such songs ensuring that at least one of the songs, if not more, get stuck in the listeners’ heads, and making all of the songs with the same hook, as long as the similarity is subtle enough, more popular as a result. It is hard to say that there are any losers if everyone gets paid and the hook is an enjoyable one, even if it makes many songs sound the same, largely because there are many similarities between them that the songwriters and producers do not make obvious, and that are hard to know unless one has an ear for patterns and an interest in doing some research, which few seem interested in.
 See, for example:
 Shewey, Don. “Whitney Houston by Whitney Houston Review”. Rolling Stone. Wenner Media LLC.