DRM and "Licensed Rights" for works that contain material licensed under CC BY 4.0

Question

CC BY 4.0 says about applying DRM (or other "Effective Technological Measures"):

No downstream restrictions. You may not […] apply any Effective Technological Measures to […] the Licensed Material if doing so restricts exercise of the Licensed Rights by any recipient of the Licensed Material.

I wonder when exactly the "exercise of the Licensed Rights" is restricted in case of CC BY.

Let’s say Alice creates a song and uses a sound effect that is licensed under CC BY 4.0. She sells this song, so she has to give attribution for the sound effect. She does not offer the sound effect in a "separate" form (i.e., she offers no download of the sound effect only).

May Alice apply DRM to the song as long as the attribution for the sound effect can be accessed ("DRM-free") by the recipients? Or have the recipients the "Licensed Right" to access ("DRM-free") the song because it contains CC-BY-licensed material?

Does the answer change if Alice modifies the sound effect (i.e., Alice creates "Adapted Material")? In the first case one could argue that recipients could extract the CC-BY-licensed sound effect from the song, but in the second case the original sound effect is no longer part of the song (i.e., recipients are not allowed to use the modified sound effect under CC BY 4.0).

Answer 1

In non-legal language, the terms of the CC-BY 4.0 are:

You are free to:

Share — copy and redistribute the material in any medium or format

Adapt — remix, transform, and build upon the material for any purpose, even commercially.

Under these terms, creating a song that includes a CC-BY licensed sound effect exercises the Adapt right.

For adaptations, the only requirements are that the adaptation must include an attribution to the author of the original work.
Adaptations are not restricted in the license terms that they use, except that they must not prevent recipients from following the attribution requirements imposed by the CC-BY license.

The downstream restrictions clause mentioned in the question applies to re-distributions of works that are licensed under CC-BY 4.0. When doing a re-distribution, of the sound effect itself, you may not use DRM techniques that would prevent others from making an adapted work or a further re-distribution.

Answer 2

The CC-BY 4.0 essential terms are:

You are free to:

Share — copy and redistribute the material in any medium or format

Adapt — remix, transform, and build upon the material for any purpose, even commercially.

So what this means is that these additional terms ...

No additional restrictions — You may not apply legal terms or technological measures that legally restrict others from doing anything the license permits.

... effectively make the CC-BY 4.0 some kind of limited copyleft license and not a pure attribution type license IMHO:

With an attribution/permissive license such as a BSD or Apache, the rights to further modify the software may not flow down automatically: I can redistribute a binary for a BSD-licensed piece of code and I am not obliged to give you the rights to further share or adapt this binary.

Here, if I read this correctly, when I include CC-BY 4.0 material everyone downstream receives all the rights of the CC-BY license, including the right to share and adapt.

This is to me essentially similar to limited copyleft terms.

And as you point it, it makes remixing something that is eventually borderline impossible when two pieces of works are effectively mixed and intertwined.

The topic is complex enough that if I were in your positions I would either stay away from using an CC-BY 4.0-licensed things unless they are unmodified or I would consult a lawyer. FWIW, CC-BY 3.0 is essentially the same