the resulting song a catchy ear worm that

[Maybo]

Soon parody videos began to appear like an acne outbreak, one of them auto-tuning my scream to a techno beat, the resulting song a catchy ear worm that itself garnered thousands of views and was later available to download from iTunes or stream on Spotify.

Source: At Home With the Horrors: 14 Tales by Sammy Scott

Does the underlined part intentionally omit "was" like "one of them (was) auto-tuning my scream to a techno beat"?

"the resulting song (was) a catchy ear worm that itself garnered thousands of views and was later available to download from iTunes or stream on Spotify"

 

[Tarheel]

If you want "was" in there you need to start a new sentence, thus: "The resulting song was...."

 

[teechar]

Does the underlined part intentionally omit "was" like "one of them (was) auto-tuning my scream to a techno beat"?

No. What you quoted "one of them auto-tuning my scream" is a (dependent) participle clause.

Participle clauses

Do you know how to use participle clauses to say information in a more economical way? Test what you know with interactive exercises and read the explanation to help you.

learnenglish.britishcouncil.org

 

[Maybo]

Is “that” intentionally omitted in “the resulting song (that) a catchy ear worm”?

 

[jutfrank]

No, but there is a linking verb (be) that's omitted:

the resulting song (being) a catchy earworm ...

You can't use 'was' so you have to use a non-finite form of 'be' instead.