Hi!
I really like this option to just ask for some artist and then Siri will play his most popular songs.
I just say: Play Busta Rhymes, Play 3oh3, Play Linkin Park, Play The Lonely Island and I have a quick "playlists" of their most popular hits and since I like them, I like everything what's popular from them.
But... maybe it's my American Siri or what, but there is NO WAY to just Play TINIE TEMPAH.
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Can you say Tinie Tempah to Siri so that she understands?
PS To workaround this I just play some selected song like: "Written in the stars" and then just ask for more from this artist.