Mercury — SketchyLogic
From NES Shooter Music (5 tracks, 3 jingles), published September 14, 2014.

Source: https://opengameart.org/content/nes-shooter-music-5-tracks-3-jingles
License: CC0 1.0 Universal
https://creativecommons.org/publicdomain/zero/1.0/

The author dedicates this music to the public domain under CC0.
The MP3 was converted from the author's WAV download; the composition is unchanged.
The original FamiTracker source is included alongside it as Mercury.ftm.
Attribution is provided as a courtesy, although CC0 does not require it.