SCP Foundation

Object Class: Keter

I can see why you'd set it as Meter, but since it affects relatively few people, I'd set it at Euclid. Remember that a lot of Euclid SCPs are able to kill!

containment procedure is established through constant monitoring by D-class personnel of radio stations and popular music streaming services (Spotify, Pandora, and SoundCloud)

I think you'd be better off by not naming the streaMing websites. Most of us know what a streaMing website is, and it just feels forced if you go out and name a few.

SCP-XXXX is the designation for a song that causes anomalies in some subjects that hear it.

Now, I am probably in the wrong here, but I don't think you should classify it as a song. Remember that the affected individuals are very delusional, and that they will of course view it as a wonderful song. However, the Foundation doesn't have any distinct proof that it is, as they can only hear static, right?
This is entirely my subjective opinion, but yeah, I thought you might want to know what I think.

SCP-XXXX seems to randomly affect individuals since groups that are known to have been subjected to SCP-XXXX have differing recollections on what was played or if anything was played at all.

I think you should phrase it so that there are only certain individuals that experience the effects of SCP-XXXX, as now you address them as random individuals.
Also, I think you should classify these people as SCP-XXXX-1, as they are a direct result of SCP-XXXX.

Also, I wouldn't classify the next steps as stages. In most "stages" there are distinct steps that all vary from each other.
In your article, the stages merely consists of different variations of the former stages. I don't think there's enough happening for it to be called a new stage.

As for the connection to Columbine, I thought it was really cool! Though I really doubt it will be taken positively by the rest of the community. I'd suggest referring to a less infamous school shooting, honestly.

But yeah, overall, I thought it was really good! There's a good pacing, the anomalies are clear and exciting and it has a somewhat distinct story behind it. Some things I'd like to see:

• An experiment log (so it's easier to imagine how it works on people)
• a little bit of rewriting (So it's a bit better formatted)
• a description from an individual affected by SCP-XXXX

Keep up the good work!