CSIX V4
Themes for Cockos REAPER
CSIX Series is a collection of ReaperThemes with a consistent appearance and a range of features, intended to improve both user experience and workflows.
CSIX supports multi-monitor awareness and is suitable for Retina, 4K as well as 1920/1080p displays using the themes at 100% or 200%
CSIX is a further development based on the dynamic/responsive default 6 theme included with REAPER 7.
CSIX is divided into four different theme series, with variants in each of the series having a common basic structure or a similar look and feel.
Read more about the CSIX Series below, or jump to the Downloads Section at the bottom of the page.
BC Series – Basic Color
Themes in the BC Series is able to display a basic colored background for all non-selected tracks, and with clear highlighting of custom colors when tracks are selected. The concept was originally created to offer themes that have an overall calm and subdued appearance, which can be preferable if you spend a lot of time with REAPER.
Furthermore, from the Theme Adjuster, there’s a cool option for adding custom color overlay to the panels, or to mix the appearance of predefined basic colors with custom colors. Due to the flexibility of using custom overlays in REAPER 7, this feature actually makes the BC themes more of a hybrid kind, check it out!
There are two themes in the BC Series: BC Extended and BC PimpedUp! In addition to the full featured BC Themes, there are two BASIC Editions. These are lighter versions that take up less space, load a little faster and don’t necessarily require as much screen width. In the BASIC Editions, some features and layouts are omitted, but basically they work in the same way.
All theme variants are continuously updated to ensure they work best possible with the latest features in REAPER. There’s also a customized CSIX Theme Adjuster that pairs exclusively with the CSIX Series. It can be used to control and recall specific settings for each theme variant and has a number of useful functions, including an extended color section with distinctive palettes and associated actions.

With the Theme Adjuster you can set rules for A-, B- and C-formatted layouts, and automatically preserve layouts when switching between theme variants. Note that theme settings will always load per theme, and if you have chosen to show specific UI elements in one theme, the same elements may be set different when switching to another.
CSIX was originally developed for high resolution displays. Many elements are designed with delicate details in mind, and fully justified when displayed in high density. In addition all variants include resources to be used as well with smaller screen sizes.



You may have noticed there’s another variant in the BC Series named PimpedUp! This theme is based upon ideas from different theming experiments. Apart from this, PimpedUp! is in fact a complete and powerful ReaperTheme that support all the latest features including monitor awareness.
MC Series – Multi Color
MC Series has a more pronounced, perhaps traditional way of showing track colors, and some elements have a stronger presence to ensure visual balance. Preferences can also be set so that REAPER draws contoured ‘peak edges’ on the displayed waveform.
All elements in the MC series are completely color streamlined, including the heavily modified V5 channel strips, and a full set of color-matching Toolbar Icons (500+), that will automatically change and correspond to the active theme variant. Furthermore, the MC Series include alternate colors for volume controls, even for the master mixer.
It is important to note that the MC series is specifically designed to use with the Color Control feature in REAPER. By having theme variants in both bright and dark tone, it’s possible to fit CSIX into different lighting environments, still preserving a natural appearance.


DM Series – Dark Mode
CSIX DM Series is especially suited for dark inverted system appearances, however the included themes works fine also for normal mode. The background of the arrangement is toned down, allowing media items and automation to stand out bright and clear. All themes in the DM Series include supplemental theme variants displaying bright inverted colors on media items.
For a full ‘dark mode’ experience, showing all control buttons and lists on dark window backgrounds, it is mandatory to run an operating system with a complete dark interface. Depending on the type of system, some OS customization may be required to achieve such UI. Here’s an example of a dark style for Windows 10. With macOS10.14 or later, there’s a native dark mode available.



Newest in CSIX:
AE Series – Advanced Editions
The AE Series includes four variants: A complete DARK theme, a genuine LIGHT theme and two hybrid theme compositions named LOOM and SLATE.
By default all variants use the narrow layout type, which provides a good overview of projects with many tracks, as well as allowing more space when working on a laptop.
The themes take full advantage of the latest theming capabilities and include 80 integrated Action Buttons using native scripts from the default REAPER installation. In addition the CSIX Theme Adjuster MyMod feature makes it easy to personalize assigned actions, change minimum heights and to fine-tune theme elements.
The AE Series includes alternate layouts such as Big Meter, which is suitable for working with multi-channels, as well as a flexible Title Track meant for inserting separators or folders with large titles.
For the mixer there are three standard layout formats: A and B with the optional setting Narrow Form also having a vertical slider for volume adjustment, and Layout C which shows the Slim Channel Strip.
Custom color overlay on control panels can be set as desired, and by having the different theme styles, it provides ample opportunity to change the entire look. Every detail has really been taken care of in these themes!
Learn more about latest features and options in the AE Series:
What’s New in CSIX ↗︎

The AE Series has several options for displaying readings and information in the TCP, allowing to have a clear overview of which tracks have been altered, while at the same time offering a compact view of multiple tracks in the project.
A lot of time has gone into developing the theme variants and the customized Theme Adjuster. All CSIX themes are constantly evolving, with improvements based on important user feedback and new ideas as they arise. At the same time, the goal is to maintain the CSIX look and feel with new features and tools that are introduced in REAPER.
To get a sense of how CSIX behaves, begin with the BASIC Editions. If you enjoy it, you can explore additional variants by choosing to support its development and continued help. For questions or inquiries, please use the contact form below or reach out via the social forums.
If you’d like to follow the social blog and read development news, check out the related thread on the REAPER Forum.
For installation, please refer to the CSIX GUIDE for step-by-step instructions, it only takes a few easy steps. From there on, updates and even new theme variants use the same basic installation, fonts, icons and latest Theme Adjuster.
Finally, once you’re familiar with the layouts and options, you’ll likely experience a highly creative workflow when working with CSIX for REAPER!

CONCEPT SIX (CSIX) GUIDE (PDF) ↗︎
Installation instructions, screenshots and useful tips.
Note: This document has not been updated to the latest CSIX changes, however, the content is still valid and explanatory:-)
See latest release info here: Changelog – April 10 – 2026 ↗︎
CSIX V4 – Features Overview (PDF)↗︎
For latest news please visit this section: What’s New in CSIX ↗︎
| CSIX – BC Series Basic Color Includes: BC Extended BC PimpedUp! | CSIX – MC Series Multi Color Includes: MC Integral MC Producer | CSIX – DM Series Dark Mode Includes: DM Onyx DM Xenon DM XenOny |
| v.4.2.9 +Adjuster v.3.7.3 | v.4.2.9 +Adjuster v.3.7.3 | v.4.2.9 +Adjuster v.3.7.3 |
CSIX – AE Series Advanced Editions Includes: AE Narrow – Dark AE Narrow – Light AE Narrow – Slate AE Narrow – Loom v.4.2.9 +Adjuster v.3.7.3 |
CSIX SERIES – COLLECTION All latest theme variants from BC, MC, DM and AE Series |
CSIX Basic and CSIX Basic Narrow Basic Editions v.4.2.9 +Adjuster v.3.7.3 |






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