The song was made by https://soundcloud.com/zkibo (the actual link should also be in the bio)

Sonic Adventure: Grounded
AU Creators — Team Grounded (Juddy - https://soundcloud.com/ocrilio, Mildred - https://soundcloud.com/mildred-f and Menoshe)
Official page — http://sonic-adventure-grounded.tumblr.com/

The most detailed description of the song can be read in another re-upload: https://soundcloud.com/kennytheknight/sonic-adventures-grounded-ost-promises-memories-rescue-your-friends-by-kibo-reupload 

The original thumbnail was found by @cupfi, for which i am grateful.

audio source: original youtube upload
audio quality: 128kbps
downloads are enabled (+sc thumbnail and mentioned description in idv3 tags)
(boring explanation start... the mp3 file has a bitrate of 320 kbps instead of 128 because blah blah blah soundcloud strongly compresses everything below wah wah wah ...boring explanation end) 

[Undertale AU - Sonic Adventure: Grounded] Promises and Memories + RESCUE your Friends

This is an unofficial non-profit archive for Kibo's old songs. Most pre-2020 undertale songs are present (except smash remixes).

The audio quality and appearance of the reuploads are as close as possible to their appearance on Kibo's old deleted accounts.

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Do not look for songs here that are not available on the official sources.

The playlist and album sections are unfinished since 2021, don't look there.

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a more tedious description of the archive:

It's just another archive for storing deleted songs. This archive contains songs by kibo that were deleted from his soundcloud accounts several years ago (the approximate release period is 2017-2021).

The priority is to provide the song with the original cover and in the most pleasant listening quality (the maximum is 320 kbps mp3). For reuploads, the download option is enabled, as it was on the original artist's page (except for the early "lazy" reuploads, since these are mp4 files with the inserted soundcloud's thumbnail).
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The archive is maintained based on personal enthusiasm, so not all deleted tracks may be present here. Also, at the request of the artist, there are no and will not be reuploads of smash remixes and some specific undertale songs.

Most of the undertale tracks have been reuploaded, all that remains is to reupload the old songs from 2017-2018 and the deltarune tracks. However, these compositions are most likely already reuploaded somewhere else in the soundcloud.

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To contact the archive owner, use the soundcloud private messaging system (@justanotherutarchive), or you can use discord - closure_and_silence

New tracks tagged #Sonic Adventure Grounded