Stormy day; It starts with few seconds of night, to emphasize and show it is a daylight. Later during composition, was trying to mimic lightning with fast darkening instead of fleshing (because I had no other option, still I think that sudden change is good enough to depict what is going on).
A nice day has started, birds are coming out. As time is passing by, there are more birds flying and singing.. Until the storm starts so birds have to hide. Rather impatiently they fly out again, as soon the rain soothes.. Day goes on, interlacing those two.
Tan function seemed to be the most effective for dramatic effects, pouring rain and bunch of birds latter coming out later. Sinus and Sawtooth for ‘the rest of the day’.