Is there a way to efficiently stop music at a certain point in the sound?

You could mute the volume of the sound, by using SoundName.Volume = 0, or, if you want it to fade out, you could use a For Loop, like so:

game.Workspace.Sound:Play() --The location of the sound

wait(10) -- Just an example, this could connect to a GUI button or anything else

for i = 0, 1, 0.1 do
    game.Workspace.Sound.Volume = i --This is assuming your volume is set to 1 already,
    wait(0.1) --the speed of the fade, this could be anything       --you could multiply the 0.1 and the iterator to 
end                                                                 --use different volumes

If you would want to fade it back in, you could do the opposite, as such:

game.Workspace.Sound:Play() --The location of the sound

wait(10) -- Just an example, this could connect to a GUI button or anything else

for i = 1, 10 do
    game.Workspace.Sound.Volume = game.Workspace.Sound.Volume + 0.1 --This is assuming your volume is set to 1 already,
    wait(0.1) --the speed of the fade, this could be anything       --you could multiply the 0.1 and the iterator to 
end                                                                 --use different volumes

Hopefully I addressed your problem correctly!

I am guessing you want to know how to stop when your sound has reached a certain point. A way to do this, is to check the sound for the TimePosition value, which shows the progress of the sound in seconds. If you want to stop the sound when it has played for 5 seconds you would do this:

sound = script.Sound --Please select your sound if you copy this script

while sound:Play() do --plays the sound
    if sound.TimePosition >= 5 then --Checks for when the sound has reached a certain point or further (because the timePosition value isn't very accurate)
        sound:Stop() --Stops the sound if it has reached 5 seconds
    end
end