is the result of song search by same mood title(like http://developer.echonest.com/api/v4/song/search?api_key=N6E4NIOVYMTHNDM8J&format=json&results=100&mood=happy) aways get the same list? is there
any limit for the search by mood? how can i get the different list by using the same mood each time?
The song search call is deterministic, but we are constantly crawling new data so the results may change slightly over time as the underlying data changes.
If you want to get a different list for the same mood each time you might consider making a static playlist of type "artist-description", or just doing the randomization on your end.