Sound of Walking Away is a song from American DJ Illenium, featuring Estonian singer Kerli. The song was first previewed at Snowglobe in December 2016, before being teased again on February 12, 2017, at Crush SF. Illenium confirmed the single in a Reddit AMA:
Sound of Walking away is [my favourite song] right now. Its an unreleased song with Kerli. I’ve been playing it out at shows.
On April 20, Illenium announced that the single would have been out on April 24, with also releasing the official cover. Illenium performed the song at Coachella 2018, with also the premiere of the music video, yet to be released. On May 11, 2018, Illenium and Kerli, with Said the Sky and 1788-L released Sound of Where'd U Go, a mashup of the two songs Sound of Walking Away and Where'd U Go.
Background and composition
I’d say probably one of the more collaborative ones was [with] Kerli. We went back and forth on a few ideas. She’s an awesome person. She’s really unique in her writing style and I love the instrumental on its own, so I was kind of picky with it. I love that track [Sound of Walking Away]. It’s one of my favourites to play out. Actually, it’s kind of an overall favourite.
On July 21, through the Instagram stories of IIZII, stage name of Everett Lee Sung, an American filmmaker, it was revealed that the song will have a music video, but the release date is still unknown. The song title also appears on Devin Schiro's "Resume" section in his website. The video is produced by Obsidiian Collective. Although not being officially released, the music video is published in Schiro's website section "Music videos". 
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- Illennium's tweet: "NEW MUSIC MONDAY!!! SO STOKED!!! @kerlimusic #soundofwalkingaway". ILLENIUMMUSIC. April 20, 2017. Twitter.
- illenium coachella 2018 full set. Nick The Revolution. April 17, 2018. youtube.
- Sound of Where'd U Go - Single (feat. Kerli) - Single. May 11, 2018. Apple Music.
- Illenium talks new album "Awake," dealing with haters and more [Exclusive Q&A]. September 21, 2017. EARMILK.
- RESUME - Devin Schiro. Retrieved on August 16, 2019.
- ILLENIUM. Retrieved on August 16, 2019.
- Billboard Dance Chart Upstarts: Illenium & Kerli, Steve Kroeger x Skye Holland & Bright Light Bright Light. May 11, 2017. Retrieved on June 30, 2017.