Being a monopoly is neither necessary nor sufficient for an anticompetitive business practice to be illegal.

A literal monopoly is not necessary for a court to determine that a firm can exert significant and durable market power over its competitors and customers.

If a firm is able to achieve and maintain a monopoly solely through lawful and reasonable means, such as producing and offering a superior product at a lower price, it is free to reap the benefits of that fairly-attained monopoly.

Acquiring all of your competitors is a good way to become a monopoly.

In what arena does Adobe compete with Apple though?

> Apple could buy all DAW companies (Steinberg, Ableton, etc) for peanuts and destroy music production on Windows if they wanted.

That constitutes monopoly and anti-competitive business practices.

"Being a monopoly" is not necessary to be in violation of US antitrust law. Merely seeking to become one via restraining trade can put you on the wrong side of the law.

But this isn't the real issue. The real issue is that the US hasn't vigorously enforced its own antitrust law in over 20 years, because a policy of "monopolies are good" was adopted in the 80s and has only gotten stronger over the years. (The Microsoft antitrust case of the 1990s was an exception.)

Well, that's exactly what we're talking about, no? Buying out all the DAW software houses would give Apple a de facto monopoly in digital audio production.

In this hypothetical world where they bought all DAW software, wouldn’t they have a monopoly on DAW software?

I don’t see how this behavior would be particularly different from John Rockefeller buying up all the means of oil production.

The hypothetical here was to become a monopoly in professional audio software tools.