psai

psai is a specialised interactive-music engine for videogames, aimed at composers and developers who need a soundtrack to react to play. It is most convincing for Unity teams building adaptive scores rather than a complete audio stack. The free engine lowers the cost of deployment, while authoring from scratch and commercial editor use require careful plan and licence decisions.

Overview

psai turns gameplay states into musical changes: intensity can be controlled, segments can be recombined automatically, playback can pause, and game logic can drive when and how music plays. That focused approach suits an interactive score whose structure changes during play, but it is not presented as a general-purpose middleware suite.

The regular and Pro editions use the same Unity engine. Pro adds the standalone Unity Edition editor, which is the route for creating psai projects from scratch, and requires Pro User Registration. A demo soundtrack and eight free themes give composers material to examine before committing to their own production.

Key features

• Adaptive playback: Intensity control and automatic segment recombination let music follow changing game conditions instead of looping a fixed track. This is the principal reason to choose psai for an interactive soundtrack.
• Unity integration: The Unity implementation is written in C# without native code, and its maker says it works on all Unity target platforms. Unity teams can therefore keep one integration approach across their chosen Unity targets.
• Native C++ SDK: A separate native SDK is available for Windows only. It is relevant to Windows-native projects, but teams targeting other native platforms should use the Unity route or consider another tool.
• Source access: Customers receive the full source code. The .NET implementation for Google protobuf is the only internally referenced DLL, which can matter to teams that need to inspect or adapt the implementation.
• Documentation and help: Manual, API documentation, tutorials, a Unity forum and a technical-support email provide several ways to get started. The posted Unity Asset Store EULA, however, says support services are supplied only under a special agreement, so formal support should not be assumed from the documentation alone.

Pricing

psai® for Unity — free

The free engine is available through the Unity Asset Store and may be used in all of a customer's Unity projects without further costs or royalties. Companies must purchase one copy per seat, so a studio's cost still scales with the number of users even though project deployment carries no additional royalty.

This plan uses the same engine as Pro, making it suitable for teams integrating psai into existing projects or evaluating runtime playback. It does not provide the standalone editor needed to create psai projects from scratch.

psai® Music Engine Pro — custom pricing

Pro is required for creating projects from scratch and includes the standalone psai® Editor plus future updates for registered Pro users. The editor download is listed for Windows and Mac and requires both Pro and Pro User Registration. The purchase is therefore aimed at composers and developers authoring new adaptive-music projects, not merely embedding the free runtime.

Commercial-use terms need attention. The editor EULA says users who have not purchased the engine through the Unity Asset Store may use the editor only non-commercially, including unlimited testing for future commercial use. Teams planning a commercial release should confirm that their purchase route covers the intended use before production begins.

Platforms

psai is available across Android, iOS, Linux, macOS and Windows in its listed platform coverage, with Unity target platforms supported by the C# engine. The native C++ SDK is Windows-only, so that broader reach applies to Unity integration rather than the separate native package.

Who it's for

psai fits videogame composers and Unity developers building music that reacts to intensity, events and gameplay logic. It is particularly sensible when a team wants source code and royalty-free use across Unity projects. It is a weaker choice for studios that need a native SDK beyond Windows, a broader audio-middleware feature set, or guaranteed support without a separate agreement.

Pros and cons

• Pro: Free Unity runtime across projects. There are no further project royalties, which helps teams shipping several Unity titles.
• Pro: Purpose-built adaptive scoring. Intensity control and segment recombination address interactive music directly.
• Pro: Full source code. Teams can inspect the implementation rather than treating the engine as an opaque binary.
• Con: Authoring is gated behind Pro. The free engine alone cannot create projects from scratch with the standalone editor.
• Con: Commercial editor restrictions. Non-Asset-Store purchases are limited to non-commercial editor use under the stated EULA.
• Con: Native SDK limited to Windows. This narrows its usefulness for non-Unity, cross-platform native development.
• Con: Seat-based company licensing. Studios must budget one copy per seat, and support is conditional on a special agreement.

Alternatives

For a wider middleware shortlist, see Game Audio Middleware.

• Amplitude Audio SDK is a free, open-source Apache-2.0 option across Android, iOS, Linux, macOS and Windows, making it preferable when permissive licensing and broad native platform coverage matter.
• Audiokinetic Wwise offers a free Indie plan for productions under a $250K budget, with unlimited sound files and a per-title licence; choose it when that production model and its commercial limits fit better.
• Reactional Engine has a free tier with forum and Discord support but requires a Reactional splash screen; it suits teams willing to accept that branding condition.
• OpenAL Soft is a free LGPL implementation of the OpenAL 3D audio API, better suited when low-level 3D audio rather than adaptive music authoring is the priority.
• SoLoud is free for commercial use under the ZLib/LibPNG licence and permits modification and redistribution.
• Steam Audio SDK is free to all developers under a licence agreement.
• Unity Version Control provides a free tier with unlimited cloud seats and 25 GB of storage, aimed at project versioning rather than music playback.
• FMOD Studio has a free Indie plan per game for qualifying budgets, making it an alternative when a broader studio workflow and its revenue and budget thresholds are acceptable.

Verdict

Choose psai if you are a Unity composer or developer whose main requirement is gameplay-responsive music, especially when royalty-free use across projects and source access are valuable. Look elsewhere if you need a non-Windows native SDK, unrestricted commercial editor use outside the Unity Asset Store, or support guaranteed without a special agreement.