I've been following and studying a particular orchestra score. I've never written for or played the Timpani or Conga before.
In the image below I see a Doit (on the Timpani) and a Fall (on the Conga).
I've tried using this articulation in Sibelius 8 but it has no affect on any percussion instrument and attempted to find a VST to use but I can't seemed to find anything. Even searching for Doit or Fall on timpani/conga using Google and YouTube brings up nothing or how it's actually performed by a real person.
It can be heard in this videoat 8:16 on the timpani and around 8:14 on the conga (It's the same score if this helps).
I have a feeling the composer or publisher has chosen to use this type of articulation for simplicity, so it could represent something else? Though, I don't think I've ever heard these sounds before in more traditional or classical music.