Non-Diegetic: Added afterwards in post production.
Crescendo: Build up of sound/music.
Diminuendo: Gradual 'die away' of music.
Sforzando: Sudden sharp sound.
Jaws-
In the scene where all the kids go swimming in the sea there is some diegetic music, when all the kids are in the sea and the boy is on his floater you get the sharks point of view this is where the non-diegetic music comes in when its a shot of the boy on the floater from under the water gradually it builds into a crescendo because it gets louder as the shark gets closer to the boy, when you get the shot of the from above the water where the shark gets the boy the music stays to the non-diegetic but as all the kids get out and the deflated floater washes up the sound comes to a complete stop.
The Godfather-
the music throughout the godfather is diegetic when he shoots them it turns to non-diegetic.