The key of B minor has become an uncommon key in pop music due to a number of factors, including cultural and historical influences, musical preferences and trends, and technological advancements in music production.
In the Western musical tradition, B minor is considered a "minor key," which is typically associated with darker, sadder, or more serious emotions. On the other hand, "major keys" such as C major or A major are often associated with brighter, happier, or more energetic emotions. Pop music, as a genre, has traditionally favored major keys and upbeat tempos, which may explain why B minor is less commonly used in this style of music.
Additionally, pop music has historically been influenced by various musical and cultural trends, which have shifted over time. For example, the 1960s and 1970s saw the rise of "folk-rock" and "soft rock" genres, which often utilized minor keys to convey a more introspective or melancholic mood. In contrast, the 1980s and 1990s saw the rise of "dance-pop" and "techno," which favored major keys and upbeat tempos. These shifting cultural and musical trends have had a significant impact on the use of different keys in pop music.
Moreover, technological advancements in music production have also played a role in the relative rarity of B minor in pop music. Today's music producers have a vast array of tools at their disposal, including synthesizers, drum machines, and digital audio workstations, which allow them to easily manipulate the tonality and mood of their productions. As a result, many pop music producers may choose to use major keys and upbeat tempos, as these are more commonly associated with the energetic, dance-oriented sound that is characteristic of the genre.
In conclusion, while the key of B minor may have been more prevalent in pop music in the past, it has become less common in recent years due to a combination of cultural and historical influences, musical preferences and trends, and technological advancements in music production. However, it is important to note that the use of different keys in music is a complex and multifaceted issue, and that many factors, including individual musical tastes, genre-specific conventions, and artistic expression, can play a role in determining the key of a particular composition.