Games like Fantasynth One
Games like Fantasynth One include Beat Saber, Paradiddle, Audioshield, Synth Riders, and Thumper. We matched them by the tags players give Fantasynth One on Steam (Audio Production, Indie, and Music): closest matches first, and among equally close ones the better-known games.

Beat Saber
Shared: VR · Music · Indie

Paradiddle
Shared: VR · Audio Production · Music

Audioshield
Shared: Indie · VR · Music

Synth Riders
Shared: VR · Indie · Music

Thumper
Shared: Indie · Music · VR

A Dance of Fire and Ice
Shared: Music · Indie

Incredibox
Shared: Music · Audio Production · Indie

Geometry Dash
Shared: Music · Indie

BOXVR
Shared: Indie · VR · Music

Soundboxing
Shared: Indie · VR · Music

AudioSurf
Shared: Indie · Music

Rhythm Doctor
Shared: Music · Indie

Spin Rhythm XD
Shared: Indie · Music · Audio Production

EXA: The Infinite Instrument
Shared: Audio Production · Indie · VR

AUDICA: Rhythm Shooter
Shared: Indie · Music · VR

Electronauts - VR Music
Shared: VR · Indie · Music

Pistol Whip
Shared: VR · Music · Indie

Audiosurf 2
Shared: Indie · Music

MUSYNX
Shared: Music · Indie

Rift of the NecroDancer
Shared: Indie · Music

Drums Rock
Shared: VR · Indie · Music

GORN
Shared: VR · Indie

Muse Dash
Shared: Music · Indie

Intralism
Shared: Indie · Music

