I have observed music duration of every kind of song. Pop music normally about 3.5 minutes long, slow rock can have longer time duration about 4.5 minutes almost similar with pop slow like on Beyonce Snowles music “Halo”. Pop slow can have longer duration, about 4.5 minutes compare with normal pop music. Pop rock can have about 4.5 minutes like on the Madonna song “Material Girls” and fast pop rock have shorter time duration, about 3.5 minutes like on Madonna Song “Like a Virgin,” Shakira song “Waka-Waka”, and Michael Jackson music , but slow pop rock can have more longer time duration like on Madonna song “Like a Prayer”.
Dangdut music that using percussion music instrument usually have longer duration more than 4 minutes and often reach of 5 minutes like India song that repeated the Lyric until three times. East traditional music also have long duration, because often stick the music out as the interlude in between the song and sometime use for dancing together for a singer with all music fans.
Music promotion take a part of this music duration so always very short time because the music duration itself are not long, and sometime just a half of minute. You can see this of music promotion duration on the right side of this blog that usually just 0.5 minute.
For normal music and easy to enjoy, to short is not good because people still enjoy the music but have stopped, too long also bad because people easy feel bored of music, even the music is not good to enjoy for longer time.