MLA 8th edition
Lastname, Firstname [or single username]. "Title of audio track." Publishing Website, Day month year posted, URL.
APA 6th edition
Lastname, Firstname [or single username]. (Year, month day posted). Title of audio track. [Audio file]. Retrieved from URL
Chicago 17th edition
Lastname, Firstname [or single username]. "Title of audio track." SoundCloud audio, length of audio track, Month day, year posted. URL.