diff --git a/src/CardinalPlugin.cpp b/src/CardinalPlugin.cpp
index ee1d5b3..3840b59 100644
--- a/src/CardinalPlugin.cpp
+++ b/src/CardinalPlugin.cpp
@@ -311,8 +311,8 @@ class CardinalPlugin : public CardinalBasePlugin
     // for base/context handling
     bool fIsActive;
     CardinalAudioDevice* fCurrentAudioDevice;
-    CardinalMidiInputDevice* fCurrentMidiInput;
-    CardinalMidiOutputDevice* fCurrentMidiOutput;
+    CardinalMidiInputDevice** fCurrentMidiInputs;
+    CardinalMidiOutputDevice** fCurrentMidiOutputs;
     uint64_t fPreviousFrame;
     Mutex fDeviceMutex;
 
@@ -327,8 +327,8 @@ public:
           fAudioBufferOut(nullptr),
           fIsActive(false),
           fCurrentAudioDevice(nullptr),
-          fCurrentMidiInput(nullptr),
-          fCurrentMidiOutput(nullptr),
+          fCurrentMidiInputs(nullptr),
+          fCurrentMidiOutputs(nullptr),
           fPreviousFrame(0)
     {
         fWindowParameters[kWindowParameterShowTooltips] = 1.0f;
@@ -397,19 +397,21 @@ public:
         fInitializer->oscPlugin = nullptr;
 #endif
 
-        {
-            const MutexLocker cml(fDeviceMutex);
-            fCurrentAudioDevice = nullptr;
-            fCurrentMidiInput = nullptr;
-            fCurrentMidiOutput = nullptr;
-        }
-
         {
             const ScopedContext sc(this);
             context->patch->clear();
             delete context;
         }
 
+        {
+            const MutexLocker cml(fDeviceMutex);
+            fCurrentAudioDevice = nullptr;
+            delete[] fCurrentMidiInputs;
+            fCurrentMidiInputs = nullptr;
+            delete[] fCurrentMidiOutputs;
+            fCurrentMidiOutputs = nullptr;
+        }
+
         if (! fAutosavePath.empty())
             rack::system::removeRecursively(fAutosavePath);
     }
@@ -434,73 +436,115 @@ protected:
         return fCurrentAudioDevice == nullptr;
     }
 
-    bool canAssignMidiInputDevice() const noexcept override
+    void assignAudioDevice(CardinalAudioDevice* const dev) noexcept override
     {
+        DISTRHO_SAFE_ASSERT_RETURN(fCurrentAudioDevice == nullptr,);
+
         const MutexLocker cml(fDeviceMutex);
-        return fCurrentMidiInput == nullptr;
+        fCurrentAudioDevice = dev;
     }
 
-    bool canAssignMidiOutputDevice() const noexcept override
+    bool clearAudioDevice(CardinalAudioDevice* const dev) noexcept override
     {
         const MutexLocker cml(fDeviceMutex);
-        return fCurrentMidiOutput == nullptr;
-    }
 
-    void assignAudioDevice(CardinalAudioDevice* const dev) noexcept override
-    {
-        DISTRHO_SAFE_ASSERT_RETURN(fCurrentAudioDevice == nullptr,);
+        if (fCurrentAudioDevice != dev)
+            return false;
 
-        const MutexLocker cml(fDeviceMutex);
-        fCurrentAudioDevice = dev;
+        fCurrentAudioDevice = nullptr;
+        return true;
     }
 
     void assignMidiInputDevice(CardinalMidiInputDevice* const dev) noexcept override
     {
-        DISTRHO_SAFE_ASSERT_RETURN(fCurrentMidiInput == nullptr,);
+        CardinalMidiInputDevice** const oldDevs = fCurrentMidiInputs;
 
-        const MutexLocker cml(fDeviceMutex);
-        fCurrentMidiInput = dev;
+        uint numDevs = 0;
+        if (oldDevs != nullptr)
+        {
+            while (oldDevs[numDevs] != nullptr)
+                ++numDevs;
+        }
+
+        CardinalMidiInputDevice** const newDevs = new CardinalMidiInputDevice*[numDevs + 2];
+
+        for (uint i=0; i<numDevs; ++i)
+            newDevs[i] = oldDevs[i];
+
+        newDevs[numDevs+0] = dev;
+        newDevs[numDevs+1] = nullptr;
+
+        {
+            const MutexLocker cml(fDeviceMutex);
+            fCurrentMidiInputs = newDevs;
+        }
+
+        delete[] oldDevs;
     }
 
     void assignMidiOutputDevice(CardinalMidiOutputDevice* const dev) noexcept override
     {
-        DISTRHO_SAFE_ASSERT_RETURN(fCurrentMidiOutput == nullptr,);
+        CardinalMidiOutputDevice** const oldDevs = fCurrentMidiOutputs;
 
-        const MutexLocker cml(fDeviceMutex);
-        fCurrentMidiOutput = dev;
-    }
+        uint numDevs = 0;
+        if (oldDevs != nullptr)
+        {
+            while (oldDevs[numDevs] != nullptr)
+                ++numDevs;
+        }
 
-    bool clearAudioDevice(CardinalAudioDevice* const dev) noexcept override
-    {
-        const MutexLocker cml(fDeviceMutex);
+        CardinalMidiOutputDevice** const newDevs = new CardinalMidiOutputDevice*[numDevs + 2];
 
-        if (fCurrentAudioDevice != dev)
-            return false;
+        for (uint i=0; i<numDevs; ++i)
+            newDevs[i] = oldDevs[i];
 
-        fCurrentAudioDevice = nullptr;
-        return true;
+        newDevs[numDevs+0] = dev;
+        newDevs[numDevs+1] = nullptr;
+
+        {
+            const MutexLocker cml(fDeviceMutex);
+            fCurrentMidiOutputs = newDevs;
+        }
+
+        delete[] oldDevs;
     }
 
-    bool clearMidiInputDevice(CardinalMidiInputDevice* const dev) noexcept override
+    void clearMidiInputDevice(CardinalMidiInputDevice* const dev) noexcept override
     {
         const MutexLocker cml(fDeviceMutex);
 
-        if (fCurrentMidiInput != dev)
-            return false;
+        CardinalMidiInputDevice** const inputs = fCurrentMidiInputs;
+        DISTRHO_SAFE_ASSERT_RETURN(inputs != nullptr,);
 
-        fCurrentMidiInput = nullptr;
-        return true;
+        for (uint i=0; inputs[i] != nullptr; ++i)
+        {
+            CardinalMidiInputDevice* const input = inputs[i];
+            if (input != dev)
+                continue;
+            for (; inputs[i+1] != nullptr; ++i)
+                inputs[i] = inputs[i+1];
+            inputs[i] = nullptr;
+            break;
+        }
     }
 
-    bool clearMidiOutputDevice(CardinalMidiOutputDevice* const dev) noexcept override
+    void clearMidiOutputDevice(CardinalMidiOutputDevice* const dev) noexcept override
     {
         const MutexLocker cml(fDeviceMutex);
 
-        if (fCurrentMidiOutput != dev)
-            return false;
+        CardinalMidiOutputDevice** const outputs = fCurrentMidiOutputs;
+        DISTRHO_SAFE_ASSERT_RETURN(outputs != nullptr,);
 
-        fCurrentMidiOutput = nullptr;
-        return true;
+        for (uint i=0; outputs[i] != nullptr; ++i)
+        {
+            CardinalMidiOutputDevice* const output = outputs[i];
+            if (output != dev)
+                continue;
+            for (; outputs[i+1] != nullptr; ++i)
+                outputs[i] = outputs[i+1];
+            outputs[i] = nullptr;
+            break;
+        }
     }
 
    /* --------------------------------------------------------------------------------------------------------
@@ -858,8 +902,11 @@ protected:
             fPreviousFrame = timePos.frame;
         }
 
-        if (fCurrentMidiInput != nullptr)
-            fCurrentMidiInput->handleMessagesFromHost(midiEvents, midiEventCount);
+        if (CardinalMidiInputDevice** inputs = fCurrentMidiInputs)
+        {
+            for (;*inputs != nullptr; ++inputs)
+                (*inputs)->handleMessagesFromHost(midiEvents, midiEventCount);
+        }
 
         if (fCurrentAudioDevice != nullptr)
         {
@@ -900,9 +947,6 @@ protected:
             std::memset(outputs[0], 0, sizeof(float)*frames);
             std::memset(outputs[1], 0, sizeof(float)*frames);
         }
-
-        if (fCurrentMidiOutput != nullptr)
-            fCurrentMidiOutput->processMessages();
     }
 
     void bufferSizeChanged(const uint32_t newBufferSize) override
diff --git a/src/PluginContext.hpp b/src/PluginContext.hpp
index 4898c09..f7cc916 100644
--- a/src/PluginContext.hpp
+++ b/src/PluginContext.hpp
@@ -117,14 +117,12 @@ public:
     ~CardinalBasePlugin() override {}
     virtual bool isActive() const noexcept = 0;
     virtual bool canAssignAudioDevice() const noexcept = 0;
-    virtual bool canAssignMidiInputDevice() const noexcept = 0;
-    virtual bool canAssignMidiOutputDevice() const noexcept = 0;
+    virtual bool clearAudioDevice(CardinalAudioDevice* dev) noexcept = 0;
     virtual void assignAudioDevice(CardinalAudioDevice* dev) noexcept = 0;
     virtual void assignMidiInputDevice(CardinalMidiInputDevice* dev) noexcept = 0;
     virtual void assignMidiOutputDevice(CardinalMidiOutputDevice* dev) noexcept = 0;
-    virtual bool clearAudioDevice(CardinalAudioDevice* dev) noexcept = 0;
-    virtual bool clearMidiInputDevice(CardinalMidiInputDevice* dev) noexcept = 0;
-    virtual bool clearMidiOutputDevice(CardinalMidiOutputDevice* dev) noexcept = 0;
+    virtual void clearMidiInputDevice(CardinalMidiInputDevice* dev) noexcept = 0;
+    virtual void clearMidiOutputDevice(CardinalMidiOutputDevice* dev) noexcept = 0;
 };
 
 #ifndef HEADLESS
diff --git a/src/PluginDriver.hpp b/src/PluginDriver.hpp
index 52ddebc..7b7ed5d 100644
--- a/src/PluginDriver.hpp
+++ b/src/PluginDriver.hpp
@@ -211,44 +211,70 @@ struct CardinalMidiInputDevice : rack::midi::InputDevice
 struct CardinalMidiOutputDevice : rack::midi::OutputDevice
 {
     CardinalBasePlugin* const fPlugin;
-    MidiEvent fQueue[128];
-    Mutex fQueueMutex;
-    uint8_t fQueueIndex;
 
     CardinalMidiOutputDevice(CardinalBasePlugin* const plugin)
-        : fPlugin(plugin),
-          fQueueIndex(0) {}
+        : fPlugin(plugin) {}
 
     std::string getName() override
     {
         return "Cardinal";
     }
 
-    void processMessages()
+    void sendMessage(const rack::midi::Message& message) override
     {
-        const MutexLocker cml(fQueueMutex);
+        const size_t size = message.bytes.size();
+        DISTRHO_SAFE_ASSERT_RETURN(size > 0,);
 
-        for (uint8_t i=0; i<fQueueIndex; ++i)
-            fPlugin->writeMidiEvent(fQueue[i]);
-
-        fQueueIndex = 0;
-    }
+        MidiEvent event;
+        event.frame = message.frame < 0 ? 0 : (message.frame - fPlugin->context->engine->getBlockFrame());
 
-    void sendMessage(const rack::midi::Message& message) override
-    {
-        if (message.bytes.size() < 3) // FIXME
-            return;
-        if ((message.bytes[0] & 0xf0) == 0xf0)
-            return;
-        if (fQueueIndex == 128)
-            return;
+        switch (message.bytes[0] & 0xF0)
+        {
+        case 0x80:
+        case 0x90:
+        case 0xA0:
+        case 0xB0:
+        case 0xE0:
+            event.size = 3;
+            break;
+        case 0xC0:
+        case 0xD0:
+            event.size = 2;
+            break;
+        case 0xF0:
+            switch (message.bytes[0] & 0x0F)
+            {
+            case 0x0:
+            case 0x4:
+            case 0x5:
+            case 0x7:
+            case 0x9:
+            case 0xD:
+                // unsupported
+                return;
+            case 0x1:
+            case 0x2:
+            case 0x3:
+            case 0xE:
+                event.size = 3;
+                break;
+            case 0x6:
+            case 0x8:
+            case 0xA:
+            case 0xB:
+            case 0xC:
+            case 0xF:
+                event.size = 1;
+                break;
+            }
+            break;
+        }
 
-        const MutexLocker cml(fQueueMutex);
+        DISTRHO_SAFE_ASSERT_RETURN(size >= event.size,);
 
-        MidiEvent& event(fQueue[fQueueIndex++]);
-        event.frame = message.frame < 0 ? 0 : (message.frame - fPlugin->context->engine->getBlockFrame());
-        event.size = 3; // FIXME
         std::memcpy(event.data, message.bytes.data(), event.size);
+
+        fPlugin->writeMidiEvent(event);
     }
 };
 
@@ -301,12 +327,8 @@ struct CardinalMidiDriver : rack::midi::Driver
         CardinalBasePlugin* const plugin = reinterpret_cast<CardinalBasePlugin*>(pluginContext->plugin);
         DISTRHO_SAFE_ASSERT_RETURN(plugin != nullptr, nullptr);
 
-        if (! plugin->canAssignMidiInputDevice())
-            throw rack::Exception("Plugin driver only allows one midi input device to be used simultaneously");
-
         CardinalMidiInputDevice* const device = new CardinalMidiInputDevice(plugin);
         device->subscribe(input);
-
         plugin->assignMidiInputDevice(device);
         return device;
     }
@@ -319,12 +341,8 @@ struct CardinalMidiDriver : rack::midi::Driver
         CardinalBasePlugin* const plugin = reinterpret_cast<CardinalBasePlugin*>(pluginContext->plugin);
         DISTRHO_SAFE_ASSERT_RETURN(plugin != nullptr, nullptr);
 
-        if (! plugin->canAssignMidiOutputDevice())
-            throw rack::Exception("Plugin driver only allows one midi output device to be used simultaneously");
-
         CardinalMidiOutputDevice* const device = new CardinalMidiOutputDevice(plugin);
         device->subscribe(output);
-
         plugin->assignMidiOutputDevice(device);
         return device;
     }
@@ -340,11 +358,9 @@ struct CardinalMidiDriver : rack::midi::Driver
         CardinalBasePlugin* const plugin = reinterpret_cast<CardinalBasePlugin*>(pluginContext->plugin);
         DISTRHO_SAFE_ASSERT_RETURN(plugin != nullptr,);
 
-        if (plugin->clearMidiInputDevice(device))
-        {
-            device->unsubscribe(input);
-            delete device;
-        }
+        plugin->clearMidiInputDevice(device);
+        device->unsubscribe(input);
+        delete device;
     }
 
     void unsubscribeOutput(int, rack::midi::Output* const output) override
@@ -358,11 +374,9 @@ struct CardinalMidiDriver : rack::midi::Driver
         CardinalBasePlugin* const plugin = reinterpret_cast<CardinalBasePlugin*>(pluginContext->plugin);
         DISTRHO_SAFE_ASSERT_RETURN(plugin != nullptr,);
 
-        if (plugin->clearMidiOutputDevice(device))
-        {
-            device->unsubscribe(output);
-            delete device;
-        }
+        plugin->clearMidiOutputDevice(device);
+        device->unsubscribe(output);
+        delete device;
     }
 };