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Building blocks are raw sound-design material, such as drones, impacts, whooshes and sci-fi blips. Describe what you need, and Reagent plays your own synths and effects with moving knobs on new tracks and records the results into your project. You need REAPER open with the Bridge running and the SWS extension installed. Building blocks start from your plugins’ own presets once Reagent has scanned them.

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What You Can Ask For

  • Length: Unless you give one, Reagent asks once per chat how long each building block should be. Whooshes never ask: they last about 6 seconds unless you say otherwise. A building block lasts from 5 seconds to 10 minutes, a whoosh can be as short as 0.3 seconds, and drones and whooshes stop at 30 seconds.
  • Plugins: Reagent picks an instrument and a few effects from the plugins you have installed. Name the ones you want, and it uses them if they’re installed.
  • Register and key: Reagent places the sound from your words, such as low for a dark drone or high for sparkly magic. Name a key, such as “in E”, or ask for low, mid and high registers to get the same sound an octave or more apart.

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How Reagent Makes Them

Each request starts with a round of very different variations, three unless you ask for another number (up to eight), named after your request, such as “Dark Spaceship 1”, “2” and “3”. No two variations in a round share a plugin chain or an instrument preset. For each one, Reagent:
  1. Loads the instrument and effects on a new track (Create plugin chain in the chat).
  2. Picks a preset for each plugin from your library (Find plugin presets and Load plugin presets).
  3. Writes the notes (Write MIDI notes) and draws automation that moves the plugins’ knobs (Draw plugin automation).
  4. Records the whole round in one take (Record building block). REAPER plays and records in real time.
In Default permissions, everything before the recording runs without asking, because it only changes the new tracks Reagent made. The recording asks first, in Auto-review too: one approval card for the whole round shows each block’s length, its tail and the total recording time. Permissions explains each mode.

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Taking One Further

Reply to a round in plain words: Reagent draws its automation lanes hidden. Ask to see them, and it shows them.

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Where They Go in Your Project

  • Source tracks: Each variation gets a muted track named Building Blocks · name (source), with its instrument, up to five effects and a safety chain that keeps the level in check.
  • Recordings: Reagent records after the end of your project, onto one Building Blocks track that it adds the first time. Each building block is one item, named with its variation, register, style, number and plugins, such as “Dark Spaceship 1 · low drone · 01 · Serum 2 → ValhallaDelay”.
  • Tails: Each building block keeps its tail until it falls below -60 dB, for up to 15 seconds.
  • Level: Each building block is peak-normalized to 0 dBFS with its take volume, so the recorded audio itself isn’t changed.
  • During a take: Reagent changes record arms, loop, count-in and the edit cursor, and puts them back afterwards. Stop keeps what was recorded.
If the project isn’t saved, the recordings go to REAPER’s default recording folder.

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Presets From Your Plugins

Reagent scans your installed plugins for their presets, so building blocks start from sounds in your own library. To start, open Settings > Plugins and click Scan plugins. Reagent also offers the scan once on each computer after setup.
  • What’s scanned: On macOS, VST3, CLAP and AU plugins. On Windows, VST3 and CLAP plugins. Reagent scans one copy of each product, VST3 first. It can’t scan VST2 plugins yet, and Windows on ARM isn’t supported yet.
  • While it runs: Plugins open one at a time in a separate helper app, and a scan can take from minutes to hours. It runs only while Reagent is open and pauses on its own while a building block records. Click Pause or Resume at any time.
  • Each plugin: The page lists each plugin with its status and preset count. Search by name or vendor, click Rescan to scan a plugin again, or Exclude from scanning to leave it out (Include brings it back). Presets already found for an excluded plugin are still used.
  • Deleting: Delete… removes every stored preset and pauses scanning. Your exclusions stay.
On macOS 15, the window of the plugin being scanned can show on your desktop, in the bottom-left corner behind your other windows. While Reagent looks for a plugin’s preset buttons, a test click can occasionally open a link from that plugin in your default browser. If you ask for building blocks before the first scan, Reagent stops and shows Open Plugins settings under its reply. Reply in the same chat to go ahead with the plugins’ default sounds instead. On a computer the scan doesn’t support, building blocks always start from the default sounds. The presets Reagent stores stay on your computer, but the names, families and tags of the presets it considers go to the AI model with your chat, and if it can’t find a plugin’s preset buttons on its own, it may send one picture of that plugin’s window (Privacy & Security).

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Documents Folder on macOS

Some plugins, FabFilter’s among them, keep their presets in your Documents folder. When a scan starts, macOS may ask whether Reagent can read it, and the scan waits for your answer. If you said no, Settings > Plugins says “macOS is blocking Reagent from your Documents folder”. Click Open System Settings, turn on Documents Folder under Reagent in Privacy & Security > Files and Folders, then click Check again. Plugins scanned while the folder was blocked are scanned again.

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Plugins Reagent Leaves Out

Reagent stops using a plugin in building blocks after it shows a licence or trial message during the scan, freezes a take, hangs REAPER while loading or stays silent in two takes. Name the plugin to use it anyway. Reagent also loads ReaVerbate in place of ReaVerb, which adds no reverb until it’s given an impulse response, unless you name ReaVerb.

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Troubleshooting

Building blocks need Bridge v0.1.4, which comes with Reagent 0.16. If a step says “This needs REAPER bridge v0.1.4 or newer”, restart the bridge so REAPER runs the updated script: click Restart bridge in the Bridge Updated notification, or Start bridge in Settings > Connectors > REAPER.
Reagent doesn’t start a take while REAPER is already playing or recording, while REAPER’s audio device won’t start, while the play rate isn’t 1.0, or while the disk is nearly full. If REAPER closed its audio device in the background, Reagent starts it first. If it still won’t start, check Preferences > Audio > Device in REAPER: the device may be unplugged or in use by another app. Fix what Reagent names and ask again.
  • “The building block’s tail was still ringing at 15 s, so it ends there with a 2 s fade-out.” Tails stop at 15 seconds. Ask for less reverb or feedback for a shorter tail.
  • “The building block was left at its recorded level: too quiet to normalize, or REAPER couldn’t read the take.” Blocks quieter than -60 dB keep their recorded level.
Hover over a status for more detail. Where Rescan shows, click it to try the plugin again.

REAPER Tools

List your installed plugins and check a plugin’s parameters.

Skills

Built-in workflows Reagent loads when a task needs them.