diff --git a/DrumMachine.pro b/DrumMachine.pro
index 7ffc1cb..24671ed 100755
--- a/DrumMachine.pro
+++ b/DrumMachine.pro
@@ -2,9 +2,9 @@ QT = core multimedia gui widgets network
 
 CONFIG += c++20
 
-release: QMAKE_CXXFLAGS_RELEASE -= -O1
-release: QMAKE_CXXFLAGS_RELEASE -= -O2
-release: QMAKE_CXXFLAGS_RELEASE += -O3 -ffast-math -march=native -mtune=native
+#release: QMAKE_CXXFLAGS_RELEASE -= -O1
+#release: QMAKE_CXXFLAGS_RELEASE -= -O2
+#release: QMAKE_CXXFLAGS_RELEASE += -O3 -ffast-math -march=native -mtune=native
 
 LIBS += -lrtmidi -lportaudio
 
@@ -14,64 +14,64 @@ SOURCES += \
     audiodecoder.cpp \
     audioformat.cpp \
     audioplayer.cpp \
-    djwidget.cpp \
     drummachinesettings.cpp \
-    drumpadwidget.cpp \
     filesmodel.cpp \
     graphrenderer.cpp \
     jsonconverters.cpp \
     main.cpp \
-    mainwindow.cpp \
     midicontainers.cpp \
     midiinwrapper.cpp \
     midioutwrapper.cpp \
-    presetdetailwidget.cpp \
     presets.cpp \
     presetsmodel.cpp \
-    previewwidget.cpp \
-    sampleswidget.cpp \
-    samplewidget.cpp \
-    scratchwidget.cpp \
-    sequencerwidget.cpp \
     synthisizer.cpp \
-    synthisizerwidget.cpp \
-    trackdeck.cpp \
-    treetotableproxymodel.cpp
+    treetotableproxymodel.cpp \
+    widgets/djwidget.cpp \
+    widgets/drumpadwidget.cpp \
+    widgets/mainwindow.cpp \
+    widgets/presetdetailwidget.cpp \
+    widgets/previewwidget.cpp \
+    widgets/sampleswidget.cpp \
+    widgets/samplewidget.cpp \
+    widgets/scratchwidget.cpp \
+    widgets/sequencerwidget.cpp \
+    widgets/synthisizerwidget.cpp \
+    widgets/trackdeck.cpp
 
 HEADERS += \
     audiodecoder.h \
     audioformat.h \
     audioplayer.h \
-    djwidget.h \
     drummachinesettings.h \
-    drumpadwidget.h \
     filesmodel.h \
     graphrenderer.h \
     jsonconverters.h \
-    mainwindow.h \
     midicontainers.h \
     midiinwrapper.h \
     midioutwrapper.h \
-    presetdetailwidget.h \
     presets.h \
     presetsmodel.h \
-    previewwidget.h \
-    sampleswidget.h \
-    samplewidget.h \
-    scratchwidget.h \
-    sequencerwidget.h \
     synthisizer.h \
-    synthisizerwidget.h \
-    trackdeck.h \
-    treetotableproxymodel.h
+    treetotableproxymodel.h \
+    widgets/djwidget.h \
+    widgets/drumpadwidget.h \
+    widgets/mainwindow.h \
+    widgets/presetdetailwidget.h \
+    widgets/previewwidget.h \
+    widgets/sampleswidget.h \
+    widgets/samplewidget.h \
+    widgets/scratchwidget.h \
+    widgets/sequencerwidget.h \
+    widgets/synthisizerwidget.h \
+    widgets/trackdeck.h
 
 FORMS += \
-    djwidget.ui \
-    drumpadwidget.ui \
-    mainwindow.ui \
-    presetdetailwidget.ui \
-    sampleswidget.ui \
-    samplewidget.ui \
-    sequencerwidget.ui \
-    synthisizerwidget.ui \
-    trackdeck.ui
+    widgets/djwidget.ui \
+    widgets/drumpadwidget.ui \
+    widgets/mainwindow.ui \
+    widgets/presetdetailwidget.ui \
+    widgets/sampleswidget.ui \
+    widgets/samplewidget.ui \
+    widgets/sequencerwidget.ui \
+    widgets/synthisizerwidget.ui \
+    widgets/trackdeck.ui
diff --git a/main.cpp b/main.cpp
index e3fe5f2..ca0b38b 100755
--- a/main.cpp
+++ b/main.cpp
@@ -5,7 +5,7 @@
 
 #include "portaudio.h"
 
-#include "mainwindow.h"
+#include "widgets/mainwindow.h"
 
 namespace {
 template<typename T>
diff --git a/synthisizer.cpp b/synthisizer.cpp
index 1021388..766d6dc 100644
--- a/synthisizer.cpp
+++ b/synthisizer.cpp
@@ -2,17 +2,17 @@
 
 #include <cmath>
 
-#include "midicontainers.h"
-
 constexpr double pi = std::acos(-1);
 
 void Synthisizer::writeSamples(frame_t *begin, frame_t *end)
 {
+    const auto volume = m_volume;
     const auto frequency = m_frequency;
+
     if (frequency)
         std::transform(begin, end, begin, [&](frame_t frame){
             std::transform(std::cbegin(frame), std::cend(frame), std::begin(frame),
-                           [value=std::sin(m_phase)](const sample_t &sample) { return sample + value; });
+                           [value=std::sin(m_phase),&volume](const sample_t &sample) { return (sample + value) * volume; });
 
             m_phase += pi*2./frameRate*m_actualFrequency;
             if (m_phase >= pi*2.)
@@ -22,14 +22,3 @@ void Synthisizer::writeSamples(frame_t *begin, frame_t *end)
         });
     m_actualFrequency = float(m_actualFrequency+m_frequency)/2.f;
 }
-
-void Synthisizer::messageReceived(const midi::MidiMessage &message)
-{
-    if (message.cmd == midi::Command::NoteOff || (message.cmd == midi::Command::NoteOn && message.velocity == 0))
-    {
-        if (m_frequency == int16_t(440.*std::pow(std::pow(2., 1./12.), message.note-48)))
-            m_frequency = 0;
-    }
-    else if (message.cmd == midi::Command::NoteOn)
-        m_frequency = 440.*std::pow(std::pow(2., 1./12.), message.note-48);
-}
diff --git a/synthisizer.h b/synthisizer.h
index 67b6f2d..1bd4eb0 100644
--- a/synthisizer.h
+++ b/synthisizer.h
@@ -1,24 +1,29 @@
 #pragma once
 
+#include <QObject>
+
 #include "audioformat.h"
 
 namespace midi { class MidiMessage; }
 
 class DrumMachineSettings;
 
-class Synthisizer
+class Synthisizer : public QObject
 {
 public:
+    float volume() const { return m_volume; }
+    void setVolume(float volume) { m_volume = volume; }
+
+    int16_t frequency() const { return m_frequency; }
     void setFrequency(int16_t frequency) { m_frequency = frequency; }
 
     void writeSamples(frame_t *begin, frame_t *end);
 
-    void messageReceived(const midi::MidiMessage &message);
-
 signals:
     void sendMidi(const midi::MidiMessage &midiMsg);
 
 private:
+    float m_volume{1.f};
     int16_t m_frequency{};
     int16_t m_actualFrequency{};
     double m_phase{};
diff --git a/synthisizerwidget.cpp b/synthisizerwidget.cpp
deleted file mode 100644
index df87c08..0000000
--- a/synthisizerwidget.cpp
+++ /dev/null
@@ -1,33 +0,0 @@
-#include "synthisizerwidget.h"
-#include "ui_synthisizerwidget.h"
-
-SynthisizerWidget::SynthisizerWidget(QWidget *parent) :
-    QWidget{parent},
-    m_ui{std::make_unique<Ui::SynthisizerWidget>()}
-{
-    m_ui->setupUi(this);
-}
-
-SynthisizerWidget::~SynthisizerWidget() = default;
-
-void SynthisizerWidget::writeSamples(frame_t *begin, frame_t *end)
-{
-    m_synthisizer.writeSamples(begin, end);
-}
-
-void SynthisizerWidget::loadSettings(DrumMachineSettings &settings)
-{
-}
-
-void SynthisizerWidget::unsendColors()
-{
-}
-
-void SynthisizerWidget::sendColors()
-{
-}
-
-void SynthisizerWidget::messageReceived(const midi::MidiMessage &message)
-{
-    m_synthisizer.messageReceived(message);
-}
diff --git a/synthisizerwidget.ui b/synthisizerwidget.ui
deleted file mode 100644
index ea3b59d..0000000
--- a/synthisizerwidget.ui
+++ /dev/null
@@ -1,32 +0,0 @@
-<?xml version="1.0" encoding="UTF-8"?>
-<ui version="4.0">
- <class>SynthisizerWidget</class>
- <widget class="QWidget" name="SynthisizerWidget">
-  <property name="geometry">
-   <rect>
-    <x>0</x>
-    <y>0</y>
-    <width>400</width>
-    <height>300</height>
-   </rect>
-  </property>
-  <property name="windowTitle">
-   <string>Form</string>
-  </property>
-  <widget class="QLabel" name="label">
-   <property name="geometry">
-    <rect>
-     <x>30</x>
-     <y>60</y>
-     <width>221</width>
-     <height>31</height>
-    </rect>
-   </property>
-   <property name="text">
-    <string>Hier könnte ihr Synthisizer stehen.</string>
-   </property>
-  </widget>
- </widget>
- <resources/>
- <connections/>
-</ui>
diff --git a/djwidget.cpp b/widgets/djwidget.cpp
similarity index 100%
rename from djwidget.cpp
rename to widgets/djwidget.cpp
diff --git a/djwidget.h b/widgets/djwidget.h
similarity index 100%
rename from djwidget.h
rename to widgets/djwidget.h
diff --git a/djwidget.ui b/widgets/djwidget.ui
similarity index 98%
rename from djwidget.ui
rename to widgets/djwidget.ui
index de64781..a0c33c6 100644
--- a/djwidget.ui
+++ b/widgets/djwidget.ui
@@ -140,7 +140,7 @@
   <customwidget>
    <class>TrackDeck</class>
    <extends>QWidget</extends>
-   <header>trackdeck.h</header>
+   <header>widgets/trackdeck.h</header>
    <container>1</container>
   </customwidget>
  </customwidgets>
diff --git a/drumpadwidget.cpp b/widgets/drumpadwidget.cpp
similarity index 99%
rename from drumpadwidget.cpp
rename to widgets/drumpadwidget.cpp
index 1a287c8..e90eefd 100644
--- a/drumpadwidget.cpp
+++ b/widgets/drumpadwidget.cpp
@@ -119,8 +119,6 @@ void DrumPadWidget::loadPresets()
 
 void DrumPadWidget::requestFinished()
 {
-    qDebug() << "called";
-
     if (!m_reply)
     {
         qWarning() << "no valid reply";
diff --git a/drumpadwidget.h b/widgets/drumpadwidget.h
similarity index 100%
rename from drumpadwidget.h
rename to widgets/drumpadwidget.h
diff --git a/drumpadwidget.ui b/widgets/drumpadwidget.ui
similarity index 95%
rename from drumpadwidget.ui
rename to widgets/drumpadwidget.ui
index 2119ad0..dedb445 100644
--- a/drumpadwidget.ui
+++ b/widgets/drumpadwidget.ui
@@ -87,19 +87,19 @@
   <customwidget>
    <class>SamplesWidget</class>
    <extends>QWidget</extends>
-   <header>sampleswidget.h</header>
+   <header>widgets/sampleswidget.h</header>
    <container>1</container>
   </customwidget>
   <customwidget>
    <class>PresetDetailWidget</class>
    <extends>QScrollArea</extends>
-   <header>presetdetailwidget.h</header>
+   <header>widgets/presetdetailwidget.h</header>
    <container>1</container>
   </customwidget>
   <customwidget>
    <class>SequencerWidget</class>
    <extends>QWidget</extends>
-   <header>sequencerwidget.h</header>
+   <header>widgets/sequencerwidget.h</header>
    <container>1</container>
   </customwidget>
  </customwidgets>
diff --git a/mainwindow.cpp b/widgets/mainwindow.cpp
similarity index 99%
rename from mainwindow.cpp
rename to widgets/mainwindow.cpp
index 09338c1..c26a8f2 100755
--- a/mainwindow.cpp
+++ b/widgets/mainwindow.cpp
@@ -37,6 +37,7 @@ MainWindow::MainWindow(QWidget *parent) :
     m_ui->setupUi(this);
 
     m_cache.setCacheDirectory("cache");
+    m_cache.setMaximumCacheSize(2ull * 1024 * 1024 * 1024);
     m_networkAccessManager.setCache(&m_cache);
 
     m_ui->drumPadWidget->injectNetworkAccessManager(m_networkAccessManager);
@@ -100,6 +101,8 @@ paDefault:
 
 MainWindow::~MainWindow()
 {
+    m_paStream = nullptr;
+
     m_decoderThread.exit();
     m_decoderThread.wait();
 }
diff --git a/mainwindow.h b/widgets/mainwindow.h
similarity index 100%
rename from mainwindow.h
rename to widgets/mainwindow.h
diff --git a/mainwindow.ui b/widgets/mainwindow.ui
similarity index 98%
rename from mainwindow.ui
rename to widgets/mainwindow.ui
index de5184b..9d5cb34 100755
--- a/mainwindow.ui
+++ b/widgets/mainwindow.ui
@@ -240,19 +240,19 @@
   <customwidget>
    <class>DjWidget</class>
    <extends>QWidget</extends>
-   <header>djwidget.h</header>
+   <header>widgets/djwidget.h</header>
    <container>1</container>
   </customwidget>
   <customwidget>
    <class>DrumPadWidget</class>
    <extends>QWidget</extends>
-   <header>drumpadwidget.h</header>
+   <header>widgets/drumpadwidget.h</header>
    <container>1</container>
   </customwidget>
   <customwidget>
    <class>SynthisizerWidget</class>
    <extends>QWidget</extends>
-   <header>synthisizerwidget.h</header>
+   <header>widgets/synthisizerwidget.h</header>
    <container>1</container>
   </customwidget>
  </customwidgets>
diff --git a/presetdetailwidget.cpp b/widgets/presetdetailwidget.cpp
similarity index 100%
rename from presetdetailwidget.cpp
rename to widgets/presetdetailwidget.cpp
diff --git a/presetdetailwidget.h b/widgets/presetdetailwidget.h
similarity index 100%
rename from presetdetailwidget.h
rename to widgets/presetdetailwidget.h
diff --git a/presetdetailwidget.ui b/widgets/presetdetailwidget.ui
similarity index 100%
rename from presetdetailwidget.ui
rename to widgets/presetdetailwidget.ui
diff --git a/previewwidget.cpp b/widgets/previewwidget.cpp
similarity index 100%
rename from previewwidget.cpp
rename to widgets/previewwidget.cpp
diff --git a/previewwidget.h b/widgets/previewwidget.h
similarity index 100%
rename from previewwidget.h
rename to widgets/previewwidget.h
diff --git a/sampleswidget.cpp b/widgets/sampleswidget.cpp
similarity index 100%
rename from sampleswidget.cpp
rename to widgets/sampleswidget.cpp
diff --git a/sampleswidget.h b/widgets/sampleswidget.h
similarity index 100%
rename from sampleswidget.h
rename to widgets/sampleswidget.h
diff --git a/sampleswidget.ui b/widgets/sampleswidget.ui
similarity index 99%
rename from sampleswidget.ui
rename to widgets/sampleswidget.ui
index bb7c46e..bd1ee1a 100755
--- a/sampleswidget.ui
+++ b/widgets/sampleswidget.ui
@@ -175,7 +175,7 @@
   <customwidget>
    <class>SampleWidget</class>
    <extends>QWidget</extends>
-   <header>samplewidget.h</header>
+   <header>widgets/samplewidget.h</header>
    <container>1</container>
   </customwidget>
  </customwidgets>
diff --git a/samplewidget.cpp b/widgets/samplewidget.cpp
similarity index 100%
rename from samplewidget.cpp
rename to widgets/samplewidget.cpp
diff --git a/samplewidget.h b/widgets/samplewidget.h
similarity index 96%
rename from samplewidget.h
rename to widgets/samplewidget.h
index 2f7a69a..a617eff 100755
--- a/samplewidget.h
+++ b/widgets/samplewidget.h
@@ -63,7 +63,7 @@ public:
 
 signals:
     void chokeTriggered(int choke);
-    void startDecoding(const std::shared_ptr<QIODevice> &device);
+    void startDecoding(std::shared_ptr<QIODevice> device);
     void sendMidi(const midi::MidiMessage &midiMsg);
 
 private slots:
diff --git a/samplewidget.ui b/widgets/samplewidget.ui
similarity index 100%
rename from samplewidget.ui
rename to widgets/samplewidget.ui
diff --git a/scratchwidget.cpp b/widgets/scratchwidget.cpp
similarity index 100%
rename from scratchwidget.cpp
rename to widgets/scratchwidget.cpp
diff --git a/scratchwidget.h b/widgets/scratchwidget.h
similarity index 100%
rename from scratchwidget.h
rename to widgets/scratchwidget.h
diff --git a/sequencerwidget.cpp b/widgets/sequencerwidget.cpp
similarity index 100%
rename from sequencerwidget.cpp
rename to widgets/sequencerwidget.cpp
diff --git a/sequencerwidget.h b/widgets/sequencerwidget.h
similarity index 100%
rename from sequencerwidget.h
rename to widgets/sequencerwidget.h
diff --git a/sequencerwidget.ui b/widgets/sequencerwidget.ui
similarity index 100%
rename from sequencerwidget.ui
rename to widgets/sequencerwidget.ui
diff --git a/widgets/synthisizerwidget.cpp b/widgets/synthisizerwidget.cpp
new file mode 100644
index 0000000..b2a42cf
--- /dev/null
+++ b/widgets/synthisizerwidget.cpp
@@ -0,0 +1,46 @@
+#include "synthisizerwidget.h"
+#include "ui_synthisizerwidget.h"
+
+#include <cmath>
+
+#include "midicontainers.h"
+
+SynthisizerWidget::SynthisizerWidget(QWidget *parent) :
+    QWidget{parent},
+    m_ui{std::make_unique<Ui::SynthisizerWidget>()}
+{
+    m_ui->setupUi(this);
+
+    connect(m_ui->horizontalSliderVolume, &QSlider::valueChanged,
+            &m_synthisizer, [&synthisizer=m_synthisizer](int value){ synthisizer.setVolume(float(value) / 100.f); });
+}
+
+SynthisizerWidget::~SynthisizerWidget() = default;
+
+void SynthisizerWidget::writeSamples(frame_t *begin, frame_t *end)
+{
+    m_synthisizer.writeSamples(begin, end);
+}
+
+void SynthisizerWidget::loadSettings(DrumMachineSettings &settings)
+{
+}
+
+void SynthisizerWidget::unsendColors()
+{
+}
+
+void SynthisizerWidget::sendColors()
+{
+}
+
+void SynthisizerWidget::messageReceived(const midi::MidiMessage &message)
+{
+    if (message.cmd == midi::Command::NoteOff || (message.cmd == midi::Command::NoteOn && message.velocity == 0))
+    {
+        if (m_synthisizer.frequency() == int16_t(440.*std::pow(std::pow(2., 1./12.), message.note-48)))
+            m_synthisizer.setFrequency(0);
+    }
+    else if (message.cmd == midi::Command::NoteOn)
+        m_synthisizer.setFrequency(440.*std::pow(std::pow(2., 1./12.), message.note-48));
+}
diff --git a/synthisizerwidget.h b/widgets/synthisizerwidget.h
similarity index 100%
rename from synthisizerwidget.h
rename to widgets/synthisizerwidget.h
diff --git a/widgets/synthisizerwidget.ui b/widgets/synthisizerwidget.ui
new file mode 100644
index 0000000..37de04a
--- /dev/null
+++ b/widgets/synthisizerwidget.ui
@@ -0,0 +1,67 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<ui version="4.0">
+ <class>SynthisizerWidget</class>
+ <widget class="QWidget" name="SynthisizerWidget">
+  <property name="geometry">
+   <rect>
+    <x>0</x>
+    <y>0</y>
+    <width>400</width>
+    <height>300</height>
+   </rect>
+  </property>
+  <property name="windowTitle">
+   <string>Form</string>
+  </property>
+  <widget class="QLabel" name="label">
+   <property name="geometry">
+    <rect>
+     <x>30</x>
+     <y>60</y>
+     <width>221</width>
+     <height>31</height>
+    </rect>
+   </property>
+   <property name="text">
+    <string>Hier könnte ihr Synthisizer stehen.</string>
+   </property>
+  </widget>
+  <widget class="QSlider" name="horizontalSliderVolume">
+   <property name="geometry">
+    <rect>
+     <x>110</x>
+     <y>110</y>
+     <width>160</width>
+     <height>16</height>
+    </rect>
+   </property>
+   <property name="maximum">
+    <number>100</number>
+   </property>
+   <property name="value">
+    <number>100</number>
+   </property>
+   <property name="orientation">
+    <enum>Qt::Horizontal</enum>
+   </property>
+  </widget>
+  <widget class="QLabel" name="labelVolume">
+   <property name="geometry">
+    <rect>
+     <x>20</x>
+     <y>110</y>
+     <width>55</width>
+     <height>18</height>
+    </rect>
+   </property>
+   <property name="text">
+    <string>Volume:</string>
+   </property>
+   <property name="buddy">
+    <cstring>horizontalSliderVolume</cstring>
+   </property>
+  </widget>
+ </widget>
+ <resources/>
+ <connections/>
+</ui>
diff --git a/trackdeck.cpp b/widgets/trackdeck.cpp
similarity index 100%
rename from trackdeck.cpp
rename to widgets/trackdeck.cpp
diff --git a/trackdeck.h b/widgets/trackdeck.h
similarity index 100%
rename from trackdeck.h
rename to widgets/trackdeck.h
diff --git a/trackdeck.ui b/widgets/trackdeck.ui
similarity index 99%
rename from trackdeck.ui
rename to widgets/trackdeck.ui
index 63238f5..d642c32 100644
--- a/trackdeck.ui
+++ b/widgets/trackdeck.ui
@@ -399,13 +399,13 @@
   <customwidget>
    <class>PreviewWidget</class>
    <extends>QWidget</extends>
-   <header>previewwidget.h</header>
+   <header>widgets/previewwidget.h</header>
    <container>1</container>
   </customwidget>
   <customwidget>
    <class>ScratchWidget</class>
    <extends>QWidget</extends>
-   <header>scratchwidget.h</header>
+   <header>widgets/scratchwidget.h</header>
    <container>1</container>
   </customwidget>
  </customwidgets>