Is calling a MSG in the Army “Top” appropriate or only exclusively used for a 1SG?

I’ve always called my 1SG Top.

The first Sgt was the only one I ever called Top. The others I called by their rank.

Personally, I'm with @1SG Anonymous on this one. I call 1SG that I respect Top (unless they tell me not to), but I also refer to MSG as "Master Sergeant" or "Mass-Sarn't." To me, it's a respect thing. If I dont like you, you get no familiarity with me, and you'll only get the stone cold, half-hearted addresses and responses out of me. If I respect you, or I like you, you'll usually get something a little more familiar or more akin to camaraderie from me.

But the caveat to that is that of I am going to address you formally by rank, I would expect the same. If I call you "Top," I got no problems with P, P-A, Petey, Tony, Petri, or anything else. But if you demand a formal address because "oh, I have a rank and I earned it," then all is fair in love and war, I have one of them rank patches too, and I earned it. You may address me accordingly.

I call them by either Master Sergeant and 1st Sergeant. I called very few as Top!

Myself it’s to each it’s own my MSG in my company I address him by his full rank because of respect master sergeant. I hate addressing e5–e8 as sergeant. But my 1sg I say first sergeant my other e8 it’s hey master sergeant ( name)

well msg usually get more respect

That's mostly reserved for 1SG's. BUT, If the MSG is the SENIOR NCO in the Company, then it would apply UNLESS they CURSE you out for you calling them that. You might get a better answer if you do a correspondence course on Military Customs and Courtesy.

Military courtesy prevails. 1SG.

Not as a formal address to the senior enlisted adviser is it appropriate. We are called by rank just as you.

To me, "TOP" referred to the First Sergeant. He is the TOP soldier in that unit. I have never heard a Master Sergeant referred to as TOP, I retired in 2009 and don't know what is happening on active duty today.