Slarmoo's Box vs UltraBox: Which BeepBox Mod Fits Your Track?
Slarmoo's Box is the better choice when you want deeper envelope control, granular and ring-mod sound design, selective randomization, and up to nine-voice unisons. UltraBox is the better default when you want a broad, well-documented all-in-one BeepBox workflow for composing, custom samples, offline builds, backup, and export. Slarmoo's Box is not an unrelated competitor: it is an UltraBox fork that keeps the familiar pattern editor while adding a more experimental synthesis layer.
Quick verdict: start in UltraBox if you are still learning the BeepBox family or need a dependable end-to-end workflow. Move to Slarmoo's Box when the song calls for programmable motion, unusual modulation, denser unisons, or granular/ring-mod textures that define the arrangement.
What Is Slarmoo's Box?
Slarmoo's Box is a free, open-source browser music editor developed as a modification of UltraBox. Its official repository describes the family tree directly: Slarmoo's Box builds on UltraBox, which builds on JummBox and ultimately BeepBox. It therefore uses the recognizable note grid, patterns, channels, instruments, and URL-contained song data that BeepBox users already understand.
The fork's identity comes from sound design. Its official FAQ highlights customizable envelope speeds and bounds, random and pitch-aware envelopes, song EQ, granular synthesis, ring modulation, more envelope targets, custom unisons, and modulation techniques that can vary by pitch or note. The result is less like a basic chiptune sketchpad and more like an experimental synth environment that still speaks the BeepBox language.
That focus separates this guide from the site's general BeepBox mods guide. The overview helps users shortlist forks; this page answers the narrower entity and comparison intent: what Slarmoo's Box adds, whether it is current, and when an UltraBox user should actually switch.
Current Version and Official Slarmoo's Box Links
Verified July 25, 2026: the official patch notes list Slarmoo's Box 1.4.13, dated July 1, 2026. That release ported UltraBox 2.2.17, added selective random and selective paste shortcuts, added nine presets, and updated several FM, unison, JSON, and modulation behaviors.
The live editor, patch notes, FAQ, and source repository are the trustworthy starting points. Search results can expose archived, testing, or downstream forks, so verify the domain before opening a song or downloading anything. The official FAQ points users to an offline release page, but it also warns that offline releases may update less often than the online editor. For that reason, this guide links to the official page rather than guessing a file URL.
Slarmoo's Box vs UltraBox Feature Comparison
| Decision point | Slarmoo's Box | UltraBox |
|---|---|---|
| Best fit | Experimental sound design, complex envelopes, random modulation, granular textures, ring modulation, and dense unisons. | General composing, broad feature coverage, custom sample workflows, larger arrangements, offline packages, and documented export/backup. |
| Project relationship | An active UltraBox fork that inherits the UltraBox base and adds its own synthesis and workflow changes. | An all-in-one BeepBox mod that combines ideas from many forks into one broad editor. |
| Current checked version | 1.4.13 online release, dated July 1, 2026; patch notes say it ports UltraBox 2.2.17. | 2.2.17 official GitHub release, published June 30, 2026. |
| Envelopes and modulation | Stronger emphasis on per-envelope speed, bounds, random behavior, pitch-aware mapping, selective randomization, and extra modulation targets. | Powerful modulation inside a broader production toolkit, with a simpler choice when you do not need Slarmoo-specific behavior. |
| Effects and texture | Granular synthesis and ring modulation are central reasons to choose the fork, alongside song EQ and expanded unison behavior. | A wide selection of synthesis engines and effects suited to many chiptune and BeepBox-family arrangements. |
| Samples and learning resources | Supports inherited UltraBox capabilities, but fork-specific behavior should be checked in its current FAQ and patch notes. | Backed here by dedicated sample, SoundFont, saving, and offline download guides. |
| Migration risk | Slarmoo-specific effects and envelopes may not reproduce in an upstream editor. | Can be a stable base for new work, but cannot be assumed to understand every downstream fork setting. |
Choose Slarmoo's Box for Programmable Sound Design
Choose Slarmoo's Box when movement inside a sound matters as much as the notes. A random envelope can produce controlled variation over time, a pitch envelope can map behavior across the keyboard, and extra envelope targets let effects change as part of the composition. Granular synthesis can break audio into shifting fragments, while ring modulation can create metallic or buzzing spectra that would take more setup to approximate elsewhere.
The fork is also appealing when you like generative starting points. Version 1.4.13's selective random feature lets you randomize chosen parts of an instrument instead of replacing everything. Selective paste applies the same principle to copying. These are practical workflow improvements: you can preserve a useful oscillator or envelope while exploring a different effect chain, then compare results without rebuilding the patch.
Do not choose it merely because it has more controls. Extra modulation adds more states to understand, more places for a migrated song to differ, and more settings to document. It earns its complexity when granular processing, custom envelope behavior, song EQ, or unison design is part of the musical idea.
Choose UltraBox for the Broadest Documented Workflow
UltraBox remains the stronger default for users who want one editor to carry a track from first loop to export. It offers advanced synthesis, more channel room, custom samples, modulation, themes, and offline releases without requiring the song to revolve around a downstream fork's special features. The surrounding documentation on this site also makes common jobs easier to recover: loading samples, converting SoundFonts, saving a complete URL, backing up JSON, and choosing an offline package.
That documentation matters when a project has dependencies. A custom sample is not truly portable unless the direct file remains available. A song URL is not a complete backup if collaborators do not know which fork created it. An offline build is only trustworthy when it comes from the official release. UltraBox is the sensible base when those practical concerns matter more than experimental envelope design.
Use Slarmoo's Box when...
- You need granular or ring-mod textures.
- You want pitch-aware, random, or deeply adjustable envelopes.
- Nine-voice unisons or song EQ are core to the patch.
- You received a Slarmoo's Box song URL.
- You want selective randomization and paste workflows.
Use UltraBox when...
- You want a broad all-in-one editor.
- You are learning the BeepBox mod ecosystem.
- You need documented sample and SoundFont workflows.
- You want official desktop or standalone HTML releases.
- You prioritize predictable backup and collaboration.
Can You Move Songs Between Slarmoo's Box and UltraBox?
Treat compatibility as a controlled migration, not a guarantee. Shared lineage means basic notes, patterns, instruments, and many settings may transfer. Slarmoo-specific envelope bounds, random behavior, selective settings, granular or ring-mod effects, expanded unisons, and newer JSON fields may not sound identical in UltraBox. Moving the other direction can also change defaults because the downstream fork may interpret or expose settings differently.
- Keep the original URL and label it with the source editor and version.
- Export JSON before migrating; do not overwrite the only editable copy.
- Open a duplicate in the target editor and listen from beginning to end.
- Check effects, envelopes, unisons, custom samples, loop points, tempo, and mod channels.
- Export a reference WAV before editing so you can compare the intended sound.
- Save the migrated version under a new name and retain both editors' links.
If collaboration is the goal, tell every contributor which fork should open the canonical song. The UltraBox save and backup guide explains how to combine URLs, audio references, JSON files, and custom-sample notes into a recoverable project package.
Common Slarmoo's Box Mistakes
Opening a Slarmoo song in UltraBox and saving immediately
Listen and compare first. Once you save over the only link or JSON copy, it becomes harder to identify which fork-specific detail changed.
Assuming the online and offline versions update together
The official FAQ says the offline build tends to update every other online update. Check the official offline release page and its tag instead of assuming the online version number applies to a downloaded file.
Using randomization without preserving a working patch
Duplicate the instrument or export JSON before exploring. Selective random is safer than replacing every property, but it is still experimentation.
Treating granular synthesis as a one-click improvement
Granular effects can add motion and width, but excessive settings may blur transients or overwhelm a small chiptune mix. Compare with bypassed audio and leave room for the lead, bass, and drums.
Frequently Asked Questions
What is Slarmoo's Box?
It is a free, open-source UltraBox fork that expands the BeepBox workflow with deeper envelopes, granular synthesis, ring modulation, song EQ, custom unisons, presets, and specialized editing shortcuts.
Is Slarmoo's Box better than UltraBox?
It is better for experimental sound design and advanced envelope work. UltraBox is better as a general default with broad features and a clearer documented path for samples, saving, offline files, and collaboration.
What is the latest verified Slarmoo's Box version?
The official patch notes showed version 1.4.13, dated July 1, 2026, when checked on July 25, 2026. Because the project updates independently, verify the patch notes before relying on that number later.
Does Slarmoo's Box have an offline version?
Yes. Its official FAQ links to offline releases and notes that OS-specific versions support custom sampling while the generic HTML version lacks custom sampling support. Use that official release page rather than an unverified mirror.
Can UltraBox open Slarmoo's Box songs?
Some data may transfer because the editors share lineage, but fork-specific effects, envelopes, and settings can change. Preserve the original URL and JSON, then test a copy in UltraBox.
Where should I go next?
Use the BeepBox mods guide for the wider family, compare AbyssBox vs UltraBox for another downstream fork, or open the UltraBox tutorial hub if you want a structured learning path.
Sources and verification
Checked July 25, 2026. Version, lineage, features, offline availability, privacy, and compatibility cautions were verified against first-party pages. Community opinions informed the questions users ask but are not presented as official product claims.