I am writing a part for strings and I want a **rapid (but not instant) diminuendo across one bar from *forte* to total silence by the end of the fourth beat**. I had four possibilities in mind for conveying this to the players:

1. Just writing the words *molto dim.*
2. Adding a hairpin beneath the bar with the word *molto* just above the hairpin.
3. Writing a performance direction above the bar saying "Silence by end of bar" with the hairpin included.
4. Adding a hairpin and putting several 'P's at the end of it.

Which would be the best way of conveying what I want?