You'll have to provide reference material to support that. Not some discretionary 'I worked in UK so I was able to convince German immigration after singing Beethoven' or vice versa) but actual policy. I'm not saying you're wrong, but it's unlikely, even if it's from 50 years ago. Germany had a guest worker program
during the 50s-70s Wirstschaftswunder years, notably Koreans and Turks coming there then. The former went back, the latter stayed in numbers. For a nation that always loved its paperwork to not have a visa policy would be pretty odd.
Unfortunately, I do not have any reference material for this. Googling for changes in German visa rules in 1981 did not yield any result. It is too ancient, pre Schengen era. Without Google, I just have to depend on my memory, as I was there. I am sure there will be BRF members that will remember this era. I dug up my old and cancelled Indian passport. This shows my first tourist visa to Germany was issued by the BRD Konsulat in Liverpool on June 2, 1981. Before that Indians did not need a tourist visa to visit West Germany. I had visited Germany at least once from UK as a tourist before this date, and I did not require a tourist visa. As the visa rule was new, I remember speaking to the Consulate to clear up things.
You may say I am wrong, but does it matter? I do not sing at all, Beethoven or any thing else. My interaction with the German immigration was strictly professional. Germany always had a visa policy. It supports their economy period. Only their economy changed with time. In the 50-60s, they were a small pariah nation, destroyed by war, disliked/hated by all European nations. 1 DM was equal to 1 rupee or so in the 60s. India was a newly independent nation and did not look down upon them. Lot of profits were made in the Rourkela project. So, Indians were allowed to visit with out a visa. Indology was a popular study. This changed later on. When I was there , China was the new friend who could import a lot of things. India was into import substitution. So, India was shown as poor and backward, Indology classes went empty. Germans studied Chinese culture and language.
Regarding guest workers, this is a separate topic altogether. I was talking about visitors visa for tourists only. Indians did not ever have a "free" Gastarbeiter visa. The same for Indian students/trainees. When I came to Germany for my training in 1977, I had to get a visa that allowed me to work for payment. A visitor visa from Germany always states "No work allowed". In the early days, 60-70s, it was possible for Indians to come in as a visitor and then change the purpose of stay and become a student or a worker. I personally know many Indians that did this. This stopped completely in the 80s. For me personally, things have gone back as they were in 1977. With a US passport, I do not need a Schengen visa. They just stamp the passport and let me enter.
Regarding Koreans and Turks in your post: The Gastarbeiter program existed even during the Nazi era. I think they called it some thing else. Huge amounts of foreign workers were imported from the conquered areas to run the armament industry, while German men were in war. And I am not talking of the Jews and Russian prisoners of war, who were worked to death at that time in the armament industry. After WWII, Germany absorbed many German refugees from the Eastern areas lost, including Russia and Poland. But as the expanding industry demanded more workers, and the war had reduced able bodied German workers, they opened the doors to other nations, such as Italy, Greece, Spain, Hungary etc. As these countries developed, their citizens went back to their home countries. Some remained, and you can see this generation in the restaurants/shops that they still have. The only exception was the Turks, who remained as their economy did not prosper as much. Many Turks have also gone back, but the uneducated have remained. I have never met a Korean Gastarbeiter. There were of course many Gastarbeiter from India, Iran, Vietnam etc, that came on their own and stayed back. The restrictions on Gastarbeiter started in the early 70s, after the first oil crisis. The industry reduced its demand and it was forecast that automation will reduce future demand for unskilled workers.