Getting error_code 5 for some tracks.

Rahul - you need to give each artist with a separate artist param like so:

http://developer.echonest.com/api/v4/playlist/dynamic/create?api_key=YOUR_API_KEY&artist=KK&artist=Pritam&artist=Shefali%20Alvares&artist=Yo%20Yo%20Honey%20Singh&bucket=id:spotify-WW&limit=true&type=artist-radio

Also, again, you won't need the song_id param.

P