Capital has a narrow playlist[3] with only a few changes per week, featuring songs from the last one to two years. Unlike BBC Radio 1, Capital does not play rock, classic hits or alternative music.
//As of June 2018, the stations serve a combined weekly audience of 7.4 million listeners and target a core audience in the 15–34 age group; 57% of all listeners are within this demographic//
That age is the group of people who i did consider listen to that type of music
Capital just plays the tamer current chart stuff. capital extra plays more rnb, grime, rap, trap ( you add the next term).
Capital plays mainly female artists - a listened yesterday for a bit and heard rita ora, ariana grande, two Dua Lipa and then they felt the need for balance to play jonas brothers. It's the sort of chart stuff radio 2 might play.
Capital extra is more likely to play radio 1 extra stuff with lots of blanked out lyric's