Gravity Machine vs The Keystone
Price, ratings, monetisation and update history for both apps, side by side — with what reviewers say about each.
Gravity Machine
Create music by manipulating a miniature solar system. Fling orbs that bounce off walls, generating notes based on physics and chosen scales. Customize worlds, sounds, and tunings for unique generative compositions.
- Generative music creation
- Physics-based orb interactions
- Customizable scales and tunings
- Multiple world shapes
- AUv3 and standalone modes
- MIDI output
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A tiny solar system that plays piano. Four orbs, a gravity well, and walls that ring like bells. Fling an orb and it falls, ricochets, and plays notes. Where it hits a wall decides what it plays; the physics decide when. You don't write the music. You build a small world and curate what it sings. Gravity is a touch instrument first. Grab an orb and it follows your finger; let go and the throw becomes its velocity. Drag the gravity well and every orbit in the room bends. Set Pulse and the well breathes in time with the tempo, so chaos starts keeping a schedule. EVERYTHING LANDS IN KEY Every impact point along the boundary maps to a note of the current scale, low at one end, high at the other. Pick from 16 scales and 11 tuning systems (12-TET, just intonation, maqam, shruti and more). The scale strip along the bottom is a key-change timeline: tap a segment, change the key, and the whole world modulates on the bar. EIGHT WORLDS TO BOUNCE IN Rectangle, circle, triangle, hexagon, pentagon, octagon, diamond, star. Sharp corners ricochet hard and play jagged. Round shapes glide and play smooth. SOUND A 16-voice pluck engine through a double-bass body and reverb. Octave, key range, quantize from 1/32 to 1/2, orb-to-orb collisions on or off. Presets to start from, themes for the visuals. AUv3 AND STANDALONE Use Gravity full-screen as a standalone instrument, or load it as an AUv3 in GarageBand, AUM, Logic Pro, Cubasis, Loopy Pro and any other Audio Unit host. Each orb has its own MIDI channel, so Gravity can drive other instruments in your host. ONE PRICE No account, no ads, no in-app purchases, no data collected. Buy it once and it's yours. The same engine ships as a VST3 and AU plugin for Windows and macOS at touchmachines.com.
The Keystone
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The Keystone dials in the sound and spirit of the early-’70s Bay Area club scene to your iPhone and iPad. More than half a century later, that music is still being played—and guitarists are still chasing those tones. Connect to your audio interface, direct to your studio, powered speakers or headphone, or send to an amp and play live. Musician and developer Mike Lawson spent years performing and recording with Merl Saunders and recording/playing with musicians from that scene. The Keystone grew out of those experiences and decades of chasing the sound as a working guitarist. He created this rig from his own live and studio settings, pedals, from authentic schematics and calibrations to his own live rig. The Keystone puts a little of that magic within reach, without the vintage-gear hunt. At the center is Quackmaster III: a touch-sensitive envelope filter with the deep, vocal quack that makes this style of guitar playing so much fun. Around it are bell-like cleans, warm amplifier breakup, singing sustain, spring reverb, phase, octave and delay, even per-accurate amps with their mods. Choose from 65 factory presets or turn the knobs and find your own sound. The effects and settings, attention to details and a few Easter eggs, this is a fun to use as it is to play through. The Keystone includes both the standalone app and an AUv3 plug-in for GarageBand, Logic Pro for iPad and other compatible iOS hosts. Plug into a compatible audio interface to play through the app, or use the plug-in in your recording sessions. One purchase includes the complete rig and AUv3 plug-in for iOS. No subscriptions, no ads, no account required. Just all good things in all good time. Support: support@artistpro.com
Screenshots
Verdict
The clearest difference is price: Gravity Machine at $9.99 against The Keystone's $19.99. On ads, in-app purchases, device support and iOS requirement there is nothing between them.
Scored on Price · Rating · Positive reviews · Number of ratings · Update frequency · Ads · In-app purchases · Monetization · Best chart rank · Devices · Requires iOS
Gravity Machine costs $9.99 and The Keystone $19.99 up front. Neither carries in-app purchases, so what you see is what you pay.
| Parameter | Gravity Machine | The Keystone |
|---|---|---|
| Price | $9.99 — better | $19.99 |
| Rating | 5.0 (1 ratings) — better | — |
| Number of ratings | 1 — better | — |
| Update frequency | Weekly | — |
| Ads | No | No |
| In-app purchases | No | No |
| Monetization | Paid | — |
| Devices | iPhone, iPad, iPod | iPhone, iPad, iPod |
| Requires iOS | 15.0 | 15.0 |
| Further details — not scored | ||
| Size | 13 MB | 42 MB |
| Age rating | 4+ | 4+ |
| Developer | Touchmachines | artistpro, LLC |
In-app purchases
Gravity Machine
No in-app purchases
The Keystone
No in-app purchases









