fade-out 
noun
A film-making and broadcasting technique whereby an image is made to disappear gradually or the sound volume is gradually decreased to zero: the fade-out before each ad break...
- Primitive - and thus charming - special effects include the early use of lap dissolves (the double-exposure of a fade-out over a fade-in) to create magical transformation scenes.
- This is where Solas should have ended, with a slow fade-out on Mother's image.
- Average sound quality and rapid fade-outs characterise the record.