Dr. Fill answers one question: what fill goes here? Give it one bar of your drum loop and it plays that bar back twice — the second time with the tail replaced by a fill. Every fill is cut from your loop's own hits: nothing is synthesized, no other samples are involved, so every fill sounds exactly like your kit, at exactly your tempo.
It builds 72 fills from whatever you feed it, spread across four pages — from played-on-a-kit rudiments and linear runs to producer-style tape stops, stutter edits and chops. You audition, pick one, and take it home as audio (WAV) or as notes (MIDI).
Dr. Fill runs three ways, and they all share the same interface: as an AU or VST3 plugin inside your DAW, as a standalone app, and in the browser inside The Vault.
2 · Requirements
Mac
macOS 11 (Big Sur) or later · Intel and Apple Silicon (one universal download) · AU, VST3, standalone app
Windows
Windows 10 or 11, 64-bit, Intel/AMD processors · VST3 and standalone app · the installer adds Microsoft's WebView2 runtime automatically if your machine lacks it
Not supported
Windows 7/8 · 32-bit systems · Windows-on-ARM devices (Surface Pro X class) · AAX/Pro Tools (in the works)
Open the DMG and double-click Install Dr. Fill.pkg.
The installer lets you choose what to install: the AU plug-in (Logic Pro, GarageBand), the VST3 plug-in (Ableton Live, Cubase, FL Studio, Studio One and most others), and the standalone app. All three are selected by default.
Enter your Mac password when asked (the plug-ins install machine-wide), then restart your DAW.
Run DrFill-Setup.exe and approve the administrator prompt.
The installer places the VST3 machine-wide and the standalone app under C:\Program Files\Yurt Rock\Dr. Fill, and installs Microsoft's WebView2 runtime if it's missing (a one-time, silent step).
Plugin not showing up? Fully quit and reopen your DAW first — most hosts only scan for new plug-ins at launch. In Ableton Live: Settings → Plug-Ins → hold Alt/Option and click Rescan.
4 · Activation & licensing
Dr. Fill installs free and opens in demo mode: load loops, capture from a track, and audition all 72 fills with no time limit. Activating unlocks WAV and MIDI export, downloading, and drag-to-DAW.
Click Demo · Activate in the top-right corner of the plugin, then use either path:
Sign in with Yurt Rock — for Vault members (the membership includes every Yurt Rock plugin) and for license owners who've added their key to their account. No key to type.
Enter a serial number — the DRFL-XXXX-XXXX-XXXX-XXXX key from your purchase email. Paste it with the Paste button or ⌘V / Ctrl+V.
The chip turns green — ✓ Active — and stays active offline. Activation is per-machine with a generous machine limit.
Managing your license
In The Vault, open vault.yurtrock.com → Plug-Ins → Your Licenses. There you can see your key again (lost-key recovery is just signing in), add a purchased key to your account, see which machines are activated, and free up a machine slot with Deactivate — for example after replacing a computer.
5 · Getting audio in
Dr. Fill opens with a starter loop loaded so there's always something to hear. Three ways to work on your audio:
Capture from the track (plugin)
Insert Dr. Fill on the track that carries your drums (or on a bus/master carrying them).
Press play in your DAW so the loop is running through the plugin.
Click Capture Track. Let a few bars pass, click again to stop.
Dr. Fill finds the cleanest loop inside the take automatically and builds all 72 fills from it.
Drop a file
Drag any audio file — WAV, AIFF, MP3, FLAC — anywhere onto the window. Full-resolution audio in means full-resolution fills out. Dr. Fill reads the tempo from the filename when it's there (loop_97.wav, 120bpm) and estimates it otherwise — and if it guessed wrong, source … · fix in the header corrects it. The main BPM readout sets a play-at tempo instead — the whole phrase time-stretches (see Troubleshooting). In the plugin, loops follow your session tempo automatically — see the host chip below.
The Vault Library
The Vault Library tab browses the entire Yurt Rock catalog without leaving your DAW. Audition anything for free; Fill this loop pulls it straight into Dr. Fill. Keeping what you make from it comes with the Vault membership.
6 · The 72 fills
Fills live on four pages, switched at the top-right of the grid:
Drummer
Played on a kit: linear runs, paradiddles, flams, tom runs, snare rolls, crescendos.
Drummer II
Deeper kit vocabulary: polyrhythms, 3-against-4, triplet bashes, fills borrowed from specific traditions.
Producer
Done to the recording: tape stops, gates, stutters, reverses, chops.
Producer II
Sampler-era moves: breakbeat edits, pitch drops, Latin patterns on the bright voices, half-time flips.
Every card shows a small badge: 2♩ fills replace the last two beats of the bar; bar fills take over the whole bar. Each card's waveform is drawn from your actual audio, so you can see a fill's shape before you hear it.
7 · Auditioning
Click a card to load that fill into the phrase — the top waveform shows your bar, then your bar again with the fill in the tail.
Double-click a card to hear just the fill on its own.
Play Phrase or Space starts and stops playback.
Switching fills during playback keeps the transport position — click between two cards while the phrase loops to A/B them against the same groove without losing your place.
If the playing fill lives on a page you're not viewing, a colored dot on the page switcher shows where it is.
In the plugin, every loop auditions at your song's tempo automatically. A gold host chip next to the BPM readout shows the DAW tempo being followed; the whole phrase — bar, fills, previews and exports — time-stretches to it, so what you hear is what lands in the arrangement. It's octave-smart: a 170 BPM loop in an 85 BPM session stays on the half-time grid instead of being slowed to half speed. Typing your own play-at tempo (or ½×/2×/×) takes over manually; click the chip to follow the host again.
Punch preserved Tempo changes use a transient-preserving stretch: every hit's attack is kept untouched — never smeared or resampled — and only the space between hits is stretched, the way drum-tuned warp modes in DAWs work. Fills stay punchy even at big tempo changes.
Guided tour Click the ? button in the bottom-left corner any time — it walks through the interface step by step, highlighting each control as it goes.
8 · Multi-bar loops
Dr. Fill works on one bar. When you load a longer loop, a bar picker appears in the header above the waveform — step through with ‹ › or pick from the menu. Bar one isn't always the interesting one; try the bar with the busiest hats or the hardest backbeat and the fills inherit that energy.
9 · Export settings
The bar under the fill grid sets what you'll take home:
WAV / MIDI
WAV is the audio, exactly as you hear it. MIDI is the fill as notes — timing and dynamics mapped to your sampler, so your own drum sounds play the fill.
Full phrase / Fill only
Take the whole two-bar phrase (bar + bar-with-fill), or just the fill region. Applies to both formats.
Sample rate
44.1 / 48 / 88.2 / 96 kHz, or Match source. The rate never goes above your source's own — upsampling a 44.1k loop to 96k adds file size, not detail. In the plugin, Dr. Fill follows your session's rate automatically.
For MIDI: which sampler's key layout the notes land on (General MIDI, MPC, Maschine, Battery, SPD-SX…).
Your choices are remembered between sessions.
10 · Downloading & drag-to-DAW
In the plugin (AU / VST3) and standalone app
↓ Download saves the export silently to your Downloads folder and flashes ✓ Saved to Downloads. Repeated saves get numbered names rather than overwriting.
The gold strip along the very bottom of the window is the drag handle: grab it and pull straight into your DAW's timeline — the file lands wherever you drop it. Clicking the strip (without dragging) opens a save dialog instead.
In the desktop app and browser
↓ Download saves the file (the desktop app saves silently; the browser shows its normal download).
⣿ Drag to DAW next to it drags the export anywhere — DAW timeline, desktop, a sampler pad.
11 · The DAW workflow
Dr. Fill is a fill builder, not a synced playback instrument — its transport is deliberately its own, so you can shop for fills while your DAW is stopped. The intended loop, using Ableton Live as the example:
Insert Dr. Fill (VST3 or AU) on your drum track.
Play the track and Capture Track a few bars. Stop capture; the fills build.
Audition inside the plugin. Shortlist two or three.
Drag each candidate from the gold strip into the arrangement at the fill point (say, bar 8). The audio is cut from your own loop at your exact tempo, so it sits in time automatically.
Play the section in context and keep the winner. For MIDI: switch the export to MIDI, drag it onto a track running your drum sampler, and the fill plays through your own sounds.
Preview audio & your interface In the AU/VST3 plugin, fill previews play through the plugin's own channel — they come out of whatever audio device your DAW uses, meter and all, like any other plugin audio. In the standalone app and the browser, previews use your computer's default output — set it to your interface if they come out of the wrong speakers (Mac: System Settings → Sound; Windows: taskbar speaker icon).
12 · Troubleshooting
The tempo was detected wrong and the fills are all over the place.
Detection misses on some loops — usually by an octave (half or double time). Next to the BPM in the header, click source … · fix and type the loop's real tempo: the same audio is re-read on the right grid — nothing is stretched — and every fill rebuilds. Tips for getting it right first time: a tempo in the filename (loop_97.wav, 120bpm) is read automatically, captures from the DAW use your session tempo exactly, and a file trimmed to a clean 1- or 2-bar loop detects far more reliably.
Can I change the tempo of the loop itself?
Yes — click the main BPM readout and type a play-at tempo, or hit ½× / 2×. The whole phrase time-stretches to it (pitch preserved, attacks untouched): the bar, the fills, the previews and the WAV/MIDI exports all move together. The readout shows 97 → 120 BPM while stretched; × returns to the loop's own tempo. In the plugin this happens for you: loops follow the session tempo until you set a tempo manually, and the host chip turns following back on.
The plugin doesn't appear in my DAW after installing.
Fully quit and relaunch the DAW — most hosts scan at startup only. Ableton: Settings → Plug-Ins → make sure VST3 is enabled, then Alt/Option-click Rescan. Logic: it appears under AU → Yurt Rock (Logic occasionally needs a second launch to finish its AU validation).
Fill previews play through the wrong output (built-in speakers / display).
In the AU/VST3 plugin this was fixed in August 2026 — previews now play through the plugin's channel and follow your DAW's audio device, so if you see it, update by re-downloading from the links above. In the standalone app and browser, previews use the system default output: set it to your audio interface (Mac: System Settings → Sound → Output; Windows: taskbar speaker icon). Exported audio is unaffected either way.
The Download button "does nothing."
It saves silently to your Downloads folder and flashes ✓ Saved to Downloads on the button. If you don't see the flash, update to the latest version (re-download from the links above — updates are free and keep your activation).
Mac says the app "Requires macOS 26.0 or later."
That was a bug in builds before mid-August 2026, not a real requirement. Re-download from the Mac link above and reinstall — the current build runs on macOS 11+.
Windows: "MSVCP140.dll was not found" or a blank/error page inside the plugin window.
Both were fixed in current builds. Re-download from the Windows link above and run the installer again.
My serial says "invalid license."
Check for look-alike characters (the key uses no lowercase; paste rather than retype). If it still fails, reply to your purchase email — keys can be verified and reissued.
"Activation limit reached."
Free a slot at vault.yurtrock.com → Plug-Ins → Your Licenses → Deactivate on a machine you no longer use.
I lost my serial number.
If you added it to your Yurt Rock account, it's shown under Your Licenses. Otherwise it's in your purchase email — or reply to that email and we'll recover it.
Does updating cost anything or lose my activation?
No and no. Download the current installer from the same links, install over the old version, done.
13 · Specifications
Formats
AU (macOS) · VST3 (macOS, Windows) · Standalone app · Browser (The Vault)
macOS
11.0+ · universal binary (Intel + Apple Silicon) · notarized installer with per-format selection
Windows
10 / 11 · 64-bit · signed installer · WebView2 runtime installed automatically when missing
Audio in
WAV, AIFF, MP3, FLAC drag-and-drop · live capture through the plugin · Vault Library
Audio out
WAV 44.1–96 kHz, 16-bit (dithered) / 24-bit / 32-bit float · session-rate matching in the plugin
MIDI out
Standard MIDI file, mapped to General MIDI, MPC, Maschine, Battery, SPD-SX and more
Licensing
Serial number or Yurt Rock sign-in · works offline once activated · included with the Vault membership
14 · Support
Stuck on something this page doesn't cover? Reply to your purchase email, or reach us through yurtrock.com — a human reads everything.