Conceptual 2-sided fnf system! Don't play them as 8 keys, play them as the regular 4 keys but you swap between them or play both at the same time like double notes Play some random song on your device and try to pretend you're playing it as an fnf song and some parts of the song are either the left side or the right side, and dramatic parts you play both at the same time
If you're on PC, to hold down all 8 notes at once--or play two different close keys like DF and CV together-- put your middIe finger between D and F and your index finger between C and V. This goes for both sides. Mobile is only allowed to do one note at once, and has no hold notes. The former is because of Scratch jankiness, and the latter is because I was too lazy.