It really depends on how low the bitrate is. A change from 320kbps (the highest “near-CD” bitrate that .mp3 supports) to 128kbps (standard .mp3) won’t make a huge difference, but a change from 160 to 75 will likely make a big difference… Bitrate tends to be a game of diminishing returns, where a difference between 96kbps and 128kbps is typically noticeable, even by laypeople… But a difference between 320kbps and 640kbps is harder to hear, (or makes no difference at all), even though it’s a much bigger jump between numbers. As the bitrate continues to increase, you get fewer and fewer benefits while your file size begins to balloon.

To be clear, there is a lot of snake oil in the audiophile world. I’m not denying that. I work in audio, (peep my username), and spend a lot of time dispelling snake oil myths as part of my job. My current audio rig is easily a quarter million dollars, and is located in an acoustically treated room, because it’s built for an entire audience. I’ve also worked in recording and system design. So I’m probably fairly qualified to speak about this specific topic…

Like lots of snake oil, the bitrate conversation is built upon grains of truth; Just enough to be convincing to someone who only has a surface level understanding of the underlying principles. And audiophiles tend to focus a lot on hardware and manufacturer’s claims, instead of studying what makes that hardware work… Which makes them particularly susceptible to snake oil myths, oftentimes perpetuated by the manufacturers to sell more expensive products to unsuspecting customers. An extreme “low vs lower” bitrate difference is one of the few things that laypeople will be able to identify when presented with an A/B test. In fact, low bitrate comparisons are often used by scummy audiophile companies as a bad-faith “here’s what our competitors sound like, vs what we sound like” example. And to be clear, reducing from ~160kbps to ~75kbps is an extreme difference.

I want you to think of the most crunchy and heavily compressed “downloaded from limewire on the family computer for your iPod” .mp3 file you’ve ever heard. Full of artifacts, absolutely no high end, sounds like it was recorded with a landline phone, and it crackles when the kick drum peaks. That was probably at least 96kbps, because that’s the lowest bitrate that .mp3 compression supports by default. And that’s after the mp3 compression algorithm has done its lossy “eh, people probably don’t care about this particular frequency” thing. 75kbps is crazy low, and you’ll undoubtedly hear the compression as a result. But again, increasing bitrates will have diminishing returns as the number continues to climb. Going from 75kbps to 160kbps will be a marked improvement, but going from 160kbps to 320kbps will be a much smaller change.

The reason audiophiles tend to have difficulty with (or even completely fail at) identifying different bitrates is because audiophiles live in a magical land where going from 1200kbps (high-end FLAC quality) to 1411kbps (uncompressed CD quality) makes a noticeable difference. In 99.9% of cases it doesn’t make any difference at all, (because again, diminishing returns) but audiophiles will swear that the 1411kbps sounds better simply because the number is bigger. Again, the snake oil is built upon grains of truth, (differences in low bitrates are immediately noticeable) but only enough to be convincing to people who don’t understand the underlying principles, (at a certain point, bitrate stops impacting audio quality and only makes your file size bigger).

All of this is to say that yes, the posted bitrate of 75kbps is laughably low. And even laypeople will absolutely be able to hear a difference between the two in an A/B comparison. Because as the bitrate approaches 0, the differences get more and more apparent. And (at least when compared to things like FLAC and CD quality) 75kbps is remarkably close to 0.

Lossy at what bitrate?

That is just such a broad statement to make that is not always true.

Opus @ 160 kbps is like MP3 at 320 kbps IIRC.

I don't know what 75 kbps opus sounds like, but I can tell you how 32 kbps sounds. Versus mp3 at that bitrate, it sounds actually listenable, while mp3 sounds like you're underwater.

All things considered, the Spotify songs probably sound fine at 75.

https://listening-test.coresv.net/results.htm#list10 via https://opus-codec.org/comparison/

It is that much better.