diff --git a/source/dsp/controller_attach.cpp b/source/dsp/controller_attach.cpp
index 621ee3a..7c031e8 100644
--- a/source/dsp/controller_attach.cpp
+++ b/source/dsp/controller_attach.cpp
@@ -33,6 +33,7 @@ namespace zlDSP {
 
     void ControllerAttach::parameterChanged(const juce::String &parameterID, float newValue) {
         if (parameterID == splitType::ID) {
+            newValue = std::min(newValue, static_cast<float>(splitType::tsteady));
             controllerRef.setType(static_cast<splitType::stype>(newValue));
             triggerAsyncUpdate();
         } else if (parameterID == mix::ID) {
diff --git a/source/dsp/dsp_definitions.hpp b/source/dsp/dsp_definitions.hpp
index d39fe94..0555a81 100644
--- a/source/dsp/dsp_definitions.hpp
+++ b/source/dsp/dsp_definitions.hpp
@@ -73,7 +73,7 @@ namespace zlDSP {
         auto static constexpr ID = "split_type";
         auto static constexpr name = "Split Type";
         inline auto static const choices = juce::StringArray{
-            "Left Right", "Mid Side", "Low High", "Transient Steady"
+            "Left Right", "Mid Side", "Low High", "Transient Steady", "", "", "", ""
         };
         int static constexpr defaultI = 0;
 
diff --git a/source/gui/combobox/combobox.hpp b/source/gui/combobox/combobox.hpp
index 4b4a6ad..f6b8f8a 100644
--- a/source/gui/combobox/combobox.hpp
+++ b/source/gui/combobox/combobox.hpp
@@ -14,5 +14,6 @@
 #include "compact_figure_combobox/compact_figure_combobox.hpp"
 #include "left_right_combobox/left_right_combobox.hpp"
 #include "click_combobox/click_combobox.hpp"
+#include "combobox_sub_attachment.hpp"
 
 #endif //ZLINTERFACE_COMBOBOX_H
diff --git a/source/gui/combobox/combobox_sub_attachment.hpp b/source/gui/combobox/combobox_sub_attachment.hpp
new file mode 100644
index 0000000..0fc9b44
--- /dev/null
+++ b/source/gui/combobox/combobox_sub_attachment.hpp
@@ -0,0 +1,75 @@
+// Copyright (C) 2024 - zsliu98
+// This file is part of ZLSplitter
+//
+// ZLSplitter is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version.
+//
+// ZLSplitter is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License along with ZLSplitter. If not, see <https://www.gnu.org/licenses/>.
+
+#ifndef COMBOBOX_SUB_ATTACHMENT_HPP
+#define COMBOBOX_SUB_ATTACHMENT_HPP
+
+#include <juce_audio_processors/juce_audio_processors.h>
+#include <juce_gui_basics/juce_gui_basics.h>
+
+namespace zlInterface {
+    class ComboBoxSubAttachment final : private juce::ComboBox::Listener {
+    public:
+        ComboBoxSubAttachment(const juce::AudioProcessorValueTreeState &stateToUse,
+                              const juce::String &parameterID,
+                              juce::ComboBox &combo,
+                              const int numItem)
+            : comboBox(combo),
+              storedParameter(*(stateToUse.getParameter(parameterID))),
+              numItems(numItem),
+              attachment(*(stateToUse.getParameter(parameterID)),
+                         [this](const float f) { setValue(f); },
+                         stateToUse.undoManager) {
+            sendInitialUpdate();
+            comboBox.addListener(this);
+        }
+
+        ~ComboBoxSubAttachment() override {
+            comboBox.removeListener(this);
+        }
+
+        /** Call this after setting up your combo box in the case where you need to do
+            extra setup after constructing this attachment.
+        */
+        void sendInitialUpdate() {
+            attachment.sendInitialUpdate();
+        }
+
+    private:
+        void setValue(const float newValue) {
+            const auto normValue = storedParameter.convertTo0to1(newValue);
+            const auto index = std::min(juce::roundToInt(normValue * static_cast<float>(numItems - 1)),
+                                        comboBox.getNumItems() - 1);
+
+            if (index == comboBox.getSelectedItemIndex()) return;
+
+            const juce::ScopedValueSetter<bool> svs(ignoreCallbacks, true);
+            comboBox.setSelectedItemIndex(index, juce::sendNotificationSync);
+        }
+
+        void comboBoxChanged(juce::ComboBox *) override {
+            if (ignoreCallbacks)
+                return;
+
+            const auto selected = static_cast<float>(comboBox.getSelectedItemIndex());
+            const auto newValue = numItems > 1
+                                      ? selected / static_cast<float>(numItems - 1)
+                                      : 0.0f;
+            attachment.setValueAsCompleteGesture(storedParameter.convertFrom0to1(newValue));
+        }
+
+        juce::ComboBox &comboBox;
+        juce::RangedAudioParameter &storedParameter;
+        int numItems;
+        juce::ParameterAttachment attachment;
+        bool ignoreCallbacks = false;
+    };
+}
+
+#endif //COMBOBOX_SUB_ATTACHMENT_HPP
diff --git a/source/panel/top_panel/top_panel.cpp b/source/panel/top_panel/top_panel.cpp
index e94dace..2ba963a 100644
--- a/source/panel/top_panel/top_panel.cpp
+++ b/source/panel/top_panel/top_panel.cpp
@@ -25,10 +25,9 @@ namespace zlPanel {
           tsIcon(juce::Drawable::createFromImageData(BinaryData::transientsteady_svg,
                                                      BinaryData::transientsteady_svgSize)),
           swapButton("", base),
-          splitBox({lrIcon.get(), msIcon.get(), lhIcon.get(), tsIcon.get()}, base) {
+          splitBox({lrIcon.get(), msIcon.get(), lhIcon.get(), tsIcon.get()}, base),
+          boxAttachment(processor.parameters, zlDSP::splitType::ID, splitBox.getBox(), zlDSP::splitType::choices.size()) {
         attach({&swapButton.getButton()}, {zlDSP::swap::ID}, processor.parameters, buttonAttachments);
-        attach({&splitBox.getBox()}, {zlDSP::splitType::ID}, processor.parameters, boxAttachments);
-
         addAndMakeVisible(logoPanel);
 
         swapButton.getLAF().enableShadow(false);
diff --git a/source/panel/top_panel/top_panel.hpp b/source/panel/top_panel/top_panel.hpp
index 1438f61..153ef2d 100644
--- a/source/panel/top_panel/top_panel.hpp
+++ b/source/panel/top_panel/top_panel.hpp
@@ -34,7 +34,7 @@ namespace zlPanel {
         zlInterface::CompactFigureCombobox splitBox;
 
         juce::OwnedArray<juce::AudioProcessorValueTreeState::ButtonAttachment> buttonAttachments;
-        juce::OwnedArray<juce::AudioProcessorValueTreeState::ComboBoxAttachment> boxAttachments;
+        zlInterface::ComboBoxSubAttachment boxAttachment;
     };
 } // zlPanel