Williams has a thud-clunk sound, early Gottlieb a loud ringing bell, later great sounding chimes. There is a difference.
(I still prefer Williams)

& later Chicago coins used a doorbell --- really.

What was the first year Gottlieb used chimes? I prefer them over bells

I haven't submitted any ratings, but I do agree there is a difference in their sounds with the different bells and chimes. IMO, the mid-to-late 70s Bally chimes are the absolute best -- beautiful clean tones that complement each other, and are at just the right volume. (example: Sky Kings, Power Play, Mata Hari, Eight Ball, Evel Knievel, etc.)

On Sing Along depending on have many colored numbers a player has made, the game has a certain distinct melody when a player lands the ball in the holes and the game starts jumping holes and counting points.

I like the way King of Diamonds sounds to me when I am playing it. Spin a Card and Flip a Card sounds different with all the spin relays clicking etc.

Don't rush when you get to the sound rating section and put in some time to listen to your EM's closely. You will be surprised to learn how each one has its own unique way of sounding off, especially if a player gets a real good game and makes special and starts popping like crazy. The knocker has always been one of my best sounds to hear on an EM.

I always rate bells higher than chimes.

I left the sound category blank on the EM games I rated, but I think as long as you are consistent it's not going to matter.

Williams and Bally bells are pretty good. Bally chimes are pretty good, Williams chimes are pretty much teh suck.

Gottlieb bells and chimes are both very good.

Sing Along, by far, is the best sounding machine in my collection. Prefer bells over chimes.

The first year Gtb. used chimes was '70. The last Gtb. Game I remember playing with bells was Mibs, and the first I remember having chimes was mini cycle, but I see chronologically there are 2 games in between them, (Road Race, Skipper), which I never played.