How do I make a 1.16.5 Forge modpack detect you in an if-do (the player) in procedure code?

I'm trying to make a mod that plays a sound where you are when you, only you, no other players, die. I have the basic Global trigger: entity dies. but I don't know what to for for the "if" in the "if-do" loop. I need a little help for this, I already asked about this, and I don't wanna tamper with the code, but if I do, I will. I really wanna do this, this has coursed my mind for a while now, but i never knew how to put it into the game without actual Java coding (I never learnt it, more less Minecraft's stuff). Please, I need help with this.