Music that plays when near a player on a certain team?

Hey there! I would start by inserting a 'Sound' into part of the killer's character. In this instance, I am going to insert it into the head. That can be done with a simple line of code:

--You will need to make a variable called "killer" in order for this to work. If you need help with this, let me know.

local sound = Instance.new("Sound")
sound.Parent = killer.Head
sound.SoundId = 12345678

There is a feature that should be built into the Sound called RollOffMaxDistance. This controls how many studs away a player can hear that sound. You can read about it here: https://developer.roblox.com/en-us/api-reference/property/Sound/RollOffMaxDistance

Then, to make only survivors hear the sound, you will want to use a LocalScript. You will want to write something similar to this:

local killer = "none"
local players = game.Players:GetChildren()
for i = 1, #players do
    if players[i].Team == "Killer" then --Change this to your team name
        killer = players[i].Name
    end
end
local player = game.Players.LocalPlayer
local killerChar = game.Workspace:FindFirstChild(killer)
local sound = killerChar.Head:WaitForChild("killerSound")

if player.Team == "Killers" then
    sound.Volume = 0
end
if player.Team == "Survivors" then
    sound.Volume = 0.5
end

I hope this helps! Don't hesitate to ask if you have any questions! ~Amanda314159

EDIT: No worries! To make the killer variable, you will want this in your main script somewhere:

--Choose killer
    local players = game.Players:GetChildren()
    local killer = players[math.random(1,#players)]
    local killerChar = game.Workspace:WaitForChild(killer.Name)
    print(killer.Name.. " is the killer!")

    --put a sound into ReplicatedStorage, and name it killerSound. This will be the killer sound.
    local sound = game.ReplicatedStorage:WaitForChild("killerSound"):Clone()
    sound.Parent = killerChar:WaitForChild("Head")

--Fire remote event

Where it says fire remote event, you will want to fire a remote event to activate a localscript containing the second chunk of code that I wrote.

--This is in a normal script within ServerScriptService
--It doesn't play any sound
for i,v in pairs(game.Teams["Killer"]:GetPlayers()) do
    local sound = Instance.new("Sound")
    sound.Parent = v.Character.Head
    sound.SoundId = "http://www.roblox.com/Asset/?id=1167182574"
    sound.RollOffMaxDistance = 60
    sound.Volume = 1
    sound:Play()
end