Most likely, you’re asking about Friday Night Bloxxin’ on Roblox, since it’s the one explicitly described as supporting 6 and 9 arrow keys in the game description and also shows up in FNF discussions as a major Roblox FNF game.

Why that fits

  • The game page for Friday Night Bloxxin’ says it supports 6 and 9 arrow keys.
  • A Roblox FNF video about it highlights special modes and note-heavy gameplay, which matches the “6 notes” idea.
  • Funky Friday is also a big Roblox FNF game, but the sources I found point more clearly to Friday Night Bloxxin’ for the 6-key/6-note style.

Other possibility

  • If you meant a game where the chart literally had 6 notes in a specific song or mod, that could be a gameplay clip rather than the game’s main mode.
  • In that case, the most likely game is still Friday Night Bloxxin’ , but the exact song or mode would matter.

Quick answer

Friday Night Bloxxin’ is the best match for “what FNF Roblox game was 6 notes”.