diff --git a/GlyphsJuke.vcxproj b/GlyphsJuke.vcxproj
index 5ed0e04..f347d0e 100644
--- a/GlyphsJuke.vcxproj
+++ b/GlyphsJuke.vcxproj
@@ -161,6 +161,7 @@
   <ItemGroup>
     <ClInclude Include="src\HiraganaMatcher.h" />
     <ClInclude Include="src\iAudioDevice.h" />
+    <ClInclude Include="src\iAudioEffect.h" />
     <ClInclude Include="src\iInputMatcher.h" />
     <ClInclude Include="src\common.h" />
     <ClInclude Include="src\ElementStore.h" />
@@ -178,6 +179,7 @@
     <ClInclude Include="src\iWritable.h" />
     <ClInclude Include="src\Logger.h" />
     <ClInclude Include="src\Lua.h" />
+    <ClInclude Include="src\Music.h" />
     <ClInclude Include="src\MusicElement.h" />
     <ClInclude Include="src\AudioDevice.h" />
     <ClInclude Include="src\MusicElementFactory.h" />
diff --git a/GlyphsJuke.vcxproj.filters b/GlyphsJuke.vcxproj.filters
index 9e195cc..4afac60 100644
--- a/GlyphsJuke.vcxproj.filters
+++ b/GlyphsJuke.vcxproj.filters
@@ -209,6 +209,12 @@
     <ClInclude Include="src\GlitchPosteffect.h">
       <Filter>Header Files</Filter>
     </ClInclude>
+    <ClInclude Include="src\iAudioEffect.h">
+      <Filter>Header Files</Filter>
+    </ClInclude>
+    <ClInclude Include="src\Music.h">
+      <Filter>Header Files</Filter>
+    </ClInclude>
   </ItemGroup>
   <ItemGroup>
     <Library Include="thirdparty\lua5.1.lib" />
diff --git a/src/AudioDevice.cc b/src/AudioDevice.cc
index bfade3b..07f74e6 100644
--- a/src/AudioDevice.cc
+++ b/src/AudioDevice.cc
@@ -21,63 +21,14 @@ gj::AudioDevice::AudioDevice() {
 gj::AudioDevice::~AudioDevice() {
   ma_device_stop(&ma_);
   ma_device_uninit(&ma_);
-
-  /* the worker thread has been exited so no lock is necessary anymore */
-
-  if (playing_) {
-    ma_decoder_uninit(&dec_);
-  }
-}
-
-void gj::AudioDevice::PlayMusic(const std::string& path, double offset) {
-  std::lock_guard _(mtx_);
-
-  if (playing_) {
-    ma_decoder_uninit(&dec_);
-  }
-  ma_decoder_config config = ma_decoder_config_init(kFormat, kChannel, kSampleRate);
-  if (ma_decoder_init_file(path.c_str(), &config, &dec_) != MA_SUCCESS) {
-    Abort("AudioDevice decoder error: "+path);
-  }
-
-  const uint64_t offset_frame = static_cast<uint64_t>(kSampleRate * offset);
-  if (ma_decoder_seek_to_pcm_frame(&dec_, offset_frame) != MA_SUCCESS) {
-    Abort("decoder seek failure");
-  }
-  playing_ = true;
-}
-
-void gj::AudioDevice::StopMusic() {
-  std::lock_guard _(mtx_);
-  if (!playing_) return;
-
-  ma_decoder_uninit(&dec_);
-  playing_ = false;
 }
 
 void gj::AudioDevice::Callback_(ma_device* ma, void* out, const void* in, ma_uint32 framecnt) {
   AudioDevice* dev = reinterpret_cast<AudioDevice*>(ma->pUserData);
   std::lock_guard _(dev->mtx_);
 
-  const double amp = dev->amp_.load();
-  const double lpf = dev->lpf_coe_.load();
-
-  float* dst = reinterpret_cast<float*>(out);
-
-  size_t wrote = 0;
-  if (dev->playing_) {
-    const ma_uint64 n = ma_decoder_read_pcm_frames(&dev->dec_, dst, framecnt);
-    if (n < framecnt) {
-      dev->playing_ = false;
-      ma_decoder_uninit(&dev->dec_);
-    }
-    wrote += n;
-  }
-
-  for (size_t i = 0; i < static_cast<size_t>(framecnt)*kChannel; ++i) {
-    dst[i] = static_cast<float>(dst[i]*amp);
-    dst[i] = static_cast<float>(dev->lpf_prev_*lpf + dst[i]*(1-lpf));
-    dev->lpf_prev_ = dst[i];
+  for (auto fx : dev->effects_) {
+    fx->Apply(reinterpret_cast<float*>(out), framecnt);
   }
   dev->time_.fetch_add(framecnt);
 }
\ No newline at end of file
diff --git a/src/AudioDevice.h b/src/AudioDevice.h
index 138612a..1851c2d 100644
--- a/src/AudioDevice.h
+++ b/src/AudioDevice.h
@@ -5,6 +5,7 @@
 #include <memory>
 #include <mutex>
 #include <string>
+#include <vector>
 
 #define NOMINMAX  /* miniaudio includes windows.h */
 #include "thirdparty/miniaudio.h"
@@ -32,14 +33,23 @@ class AudioDevice : public iAudioDevice, public iClock {
   AudioDevice();
   ~AudioDevice();
 
-  void PlayMusic(const std::string& path, double offset) override;
-  void StopMusic() override;
-
-  void SetVolume(double amp) override {
-    amp_.store(amp);
+  void AddEffect(iAudioEffect* fx) override {
+    std::lock_guard _(mtx_);
+    effects_.push_back(fx);
   }
-  void SetLpfIntensity(double v) override {
-    lpf_coe_.store(v);
+  void RemoveEffect(iAudioEffect* fx) override {
+    std::lock_guard _(mtx_);
+
+    auto itr = std::find(effects_.begin(), effects_.end(), fx);
+    if (itr == effects_.end()) return;
+    effects_.erase(itr);
+  }
+
+  uint8_t ch() const override {
+    return kChannel;
+  }
+  uint32_t sampleRate() const override {
+    return kSampleRate;
   }
 
   uint64_t now() const override {
@@ -51,16 +61,10 @@ class AudioDevice : public iAudioDevice, public iClock {
 
   ma_device ma_{0};
 
-  bool playing_ = false;
-  ma_decoder dec_{0};
-
-  std::atomic<double> amp_ = 1;
-
-  std::atomic<double> lpf_coe_  = 0;
-  float               lpf_prev_ = 0;
-
   std::atomic<uint64_t> time_;
 
+  std::vector<iAudioEffect*> effects_;
+
   static void Callback_(ma_device* ma, void* out, const void* in, ma_uint32 framecnt);
 };
 
diff --git a/src/ElementStore.h b/src/ElementStore.h
index 5dce7aa..70eac24 100644
--- a/src/ElementStore.h
+++ b/src/ElementStore.h
@@ -67,10 +67,21 @@ class ElementStore {
       performing_.end());
   }
 
-  bool IsEmpty() {
+  bool IsEmpty() const {
     return pending_.empty() && performing_.empty();
   }
 
+  size_t CountPreparings() const {
+    size_t n = 0;
+    for (const auto& e : pending_) {
+      if (!e->HasPrepared()) ++n;
+    }
+    return n;
+  }
+  size_t size() const {
+    return pending_.size() + performing_.size();
+  }
+
  private:
   const iClock* clock_;
 
diff --git a/src/InputWindowElement.h b/src/InputWindowElement.h
index 5469501..d35d605 100644
--- a/src/InputWindowElement.h
+++ b/src/InputWindowElement.h
@@ -75,6 +75,10 @@ class InputWindowElement : public iElement {
     }
   }
 
+  bool HasPrepared() const override {
+    return true;
+  }
+
  private:
   UniqPtr<iInputMatcher>  matcher_;
   UniqPtr<iElementDriver> drv_;
diff --git a/src/Music.h b/src/Music.h
new file mode 100644
index 0000000..2c95fae
--- /dev/null
+++ b/src/Music.h
@@ -0,0 +1,116 @@
+#pragma once
+
+#include <atomic>
+#include <thread>
+
+#define NOMINMAX
+#include "thirdparty/miniaudio.h"
+#undef NOMINMAX
+
+#include "common.h"
+#include "iAudioEffect.h"
+
+
+namespace gj {
+
+
+class Music : public iAudioEffect {
+ public:
+  static constexpr auto kVolumeLpf = .9f;
+
+  Music() = delete;
+  Music(Music&&) = delete;
+  Music(const Music&) = delete;
+
+  Music& operator=(Music&&) = delete;
+  Music& operator=(const Music&) = delete;
+
+  Music(const std::string& path, uint8_t ch, uint32_t srate) :
+      ch_(ch), srate_(srate), lpf_prev_(ch) {
+    const auto config = ma_decoder_config_init(ma_format_f32, ch, srate);
+
+    if (ma_decoder_init_file(path.c_str(), &config, &dec_)) {
+      Abort("decoder error: "+path);
+    }
+  }
+  ~Music() {
+    if (seeker_.joinable()) {
+      seeker_.join();
+    }
+    ma_decoder_uninit(&dec_);
+  }
+
+  void Play() {
+    playing_.store(true);
+  }
+  void Stop() {
+    playing_.store(false);
+  }
+  void Seek(double sec) {
+    if (seeker_.joinable()) {
+      seeker_.join();
+    }
+    seeking_.store(true);
+
+    const size_t frame = static_cast<size_t>(srate_*sec);
+    seeker_ = std::thread([this, frame]() {
+      if (ma_decoder_seek_to_pcm_frame(&dec_, frame) != MA_SUCCESS) {
+        Abort("decoder seek failure");
+      }
+      seeking_.store(false);
+    });
+  }
+
+  void SetVolume(float f) {
+    volume_.store(f);
+  }
+  void SetLpf(float f) {
+    lpf_.store(f);
+  }
+
+  bool IsBusy() const {
+    return seeking_.load();
+  }
+
+  void Apply(float* ptr, size_t frames) override {
+    if (seeking_.load() || !playing_.load()) return;
+
+    frames = ma_decoder_read_pcm_frames(&dec_, ptr, frames);
+
+    const float lpf    = lpf_.load();
+    const float lpfinv = 1-lpf;
+
+    const float volume = volume_.load();
+
+    const size_t n = frames * ch_;
+    for (size_t i = 0; i < frames; ++i) {
+      volume_actual_ = volume_actual_*kVolumeLpf + volume*(1-kVolumeLpf);
+
+      float* sample = &ptr[i*ch_];
+      for (uint8_t j = 0; j < ch_; ++j) {
+        sample[j]    = lpf_prev_[j]*lpf + sample[j]*volume_actual_*lpfinv;
+        lpf_prev_[j] = sample[j];
+      }
+    }
+  }
+
+ private:
+  uint8_t  ch_;
+  uint32_t srate_;
+
+  std::thread seeker_;
+
+  ma_decoder dec_{0};
+
+  std::atomic<bool> seeking_ = false;
+  std::atomic<bool> playing_ = false;
+
+  std::atomic<float> volume_ = 0;
+  std::atomic<float> lpf_    = 0;
+
+  float volume_actual_;
+  std::vector<float> lpf_prev_;
+};
+
+
+}
\ No newline at end of file
diff --git a/src/MusicElement.h b/src/MusicElement.h
index c187318..bf4d254 100644
--- a/src/MusicElement.h
+++ b/src/MusicElement.h
@@ -5,7 +5,7 @@
 #include "iAudioDevice.h"
 #include "iElement.h"
 #include "iElementDriver.h"
-#include "Texture.h"
+#include "Music.h"
 
 namespace gj {
 
@@ -31,8 +31,12 @@ public:
   MusicElement& operator=(const MusicElement&) = delete;
 
   MusicElement(Param&& p) :
-      iElement(p.period), audio_(p.audio), path_(p.path), offset_(p.offset),
+      iElement(p.period), audio_(p.audio),
+      music_(p.path, audio_->ch(), audio_->sampleRate()),
       drv_(std::move(p.driver)) {
+    music_.Seek(p.offset);
+    audio_->AddEffect(&music_);
+
     param_["volume"] = 0.;
     param_["lpf"]    = 0.;
   }
@@ -43,29 +47,29 @@ public:
     const double volume = std::get<double>(param_["volume"]);
     const double lpf    = std::get<double>(param_["lpf"]);
 
-    audio_->SetVolume(volume);
-    audio_->SetLpfIntensity(lpf);
+    music_.SetVolume(static_cast<float>(volume));
+    music_.SetLpf(static_cast<float>(lpf));
 
     if (first_) {
-      audio_->PlayMusic(path_, offset_);
+      music_.Play();
       first_ = false;
     }
   }
 
   void Finalize() override {
-    if (!first_) {
-      audio_->StopMusic();
-    }
+    audio_->RemoveEffect(&music_);
+  }
+
+  bool HasPrepared() const override {
+    return !music_.IsBusy();
   }
 
  private:
   iAudioDevice* audio_;
-  std::string   path_;
+  Music         music_;
 
   bool first_ = true;
 
-  double offset_;
-
   UniqPtr<iElementDriver> drv_;
   iElementDriver::Param   param_;
 };
diff --git a/src/TextureElement.h b/src/TextureElement.h
index 25514a2..4877a06 100644
--- a/src/TextureElement.h
+++ b/src/TextureElement.h
@@ -68,6 +68,10 @@ public:
   void Finalize() override {
   }
 
+  bool HasPrepared() const override {
+    return true;
+  }
+
  private:
   Texture tex_;
   UniqPtr<iElementDriver> drv_;
diff --git a/src/TitleScene.cc b/src/TitleScene.cc
index 67741bb..45a6f4b 100644
--- a/src/TitleScene.cc
+++ b/src/TitleScene.cc
@@ -53,6 +53,7 @@ gj::TitleScene::TitleScene(const Param& p) :
 }
 
 gj::UniqPtr<gj::iScene> gj::TitleScene::Update(Frame& frame) {
+  /* input handling */
   for (const auto c : frame.input) {
     switch (c) {
     case 'h':
@@ -62,11 +63,31 @@ gj::UniqPtr<gj::iScene> gj::TitleScene::Update(Frame& frame) {
       SelectScore_((select_index_+1)%list_.size());
       break;
     case ' ':
+      if (music_) param_.audio->RemoveEffect(music_.get());
       return param_.alloc->MakeUniq<iScene, PlayScene>(
         param_, list_[select_index_].displayName, list_[select_index_].score);
     }
   }
 
+  /* play music */
+  if (trying_play_ && !(music_ && music_->IsBusy())) {
+    if (music_) {
+      param_.audio->RemoveEffect(music_.get());
+    }
+    auto au = param_.audio;
+
+    const auto& s = list_[select_index_];
+    music_ = param_.alloc->MakeUniq<Music>(s.music, au->ch(), au->sampleRate());
+    music_->Seek(s.playOffset);
+    music_->SetVolume(.2f);
+    music_->SetLpf(.99f);
+    music_->Play();
+
+    au->AddEffect(music_.get());
+    trying_play_ = false;
+  }
+
+  /* graphics calculation */
   const uint64_t now = param_.clock->now();
 
   const int32_t w = static_cast<int32_t>(frame.w);
@@ -112,7 +133,7 @@ gj::UniqPtr<gj::iScene> gj::TitleScene::Update(Frame& frame) {
   frame.Add(&guide_);
 
   pe_.seed     = XorShift(now/period1+10);
-  pe_.maxShift = (XorShift(now/period1+7)%100/100.*2 - 1)*.1;
+  pe_.maxShift = (XorShift(now/period1+7)%100/100.*2 - 1)*.03;
   frame.Add(&pe_);
 
   return nullptr;
@@ -123,7 +144,5 @@ void gj::TitleScene::SelectScore_(size_t index) {
   score_        = Text(ConvertStrToWstr(s.displayName));
   select_index_ = index;
   
-  param_.audio->SetVolume(.5);
-  param_.audio->SetLpfIntensity(.999);
-  param_.audio->PlayMusic(s.music, s.playOffset);
+  trying_play_ = true;
 }
\ No newline at end of file
diff --git a/src/TitleScene.h b/src/TitleScene.h
index 1bb95b7..9a2d0b6 100644
--- a/src/TitleScene.h
+++ b/src/TitleScene.h
@@ -3,6 +3,7 @@
 #include "common.h"
 #include "GlitchPosteffect.h"
 #include "iScene.h"
+#include "Music.h"
 #include "Text.h"
 #include "Texture.h"
 
@@ -29,7 +30,7 @@ class TitleScene : public iScene {
     std::string displayName;
     std::string score;
     std::string music;
-    double      playOffset;
+    double      playOffset = 0;
   };
 
   Param param_;
@@ -40,13 +41,17 @@ class TitleScene : public iScene {
   Text guide_;
 
   Texture logo_;
+
+  GlitchPosteffect pe_;
   
   size_t select_index_;
   std::vector<Score> list_;
 
-  GlitchPosteffect pe_;
+  bool trying_play_ = false;
+  UniqPtr<Music> music_;
 
   void SelectScore_(size_t index);
+  void TryPlayingMusic_();
 };
 
 
diff --git a/src/common.h b/src/common.h
index 11de546..8399e54 100644
--- a/src/common.h
+++ b/src/common.h
@@ -48,10 +48,15 @@ static inline uint64_t XorShift(uint64_t x) {
 
 
 [[noreturn]]
-static inline void Abort(const std::string& msg) {
-  MessageBox(NULL, ConvertStrToWstr(msg).c_str(), L"PROGRAM ABORTED", MB_OK);
+static inline void Abort(const std::wstring& msg) {
+  MessageBox(NULL, msg.c_str(), L"PROGRAM ABORTED", MB_OK);
   std::exit(1);
 }
+[[noreturn]]
+static inline void Abort(const std::string& msg) {
+  Abort(ConvertStrToWstr(msg));
+}
+
 
 
 }
\ No newline at end of file
diff --git a/src/iAudioDevice.h b/src/iAudioDevice.h
index a38a675..5d7a087 100644
--- a/src/iAudioDevice.h
+++ b/src/iAudioDevice.h
@@ -2,6 +2,8 @@
 
 #include <string>
 
+#include "iAudioEffect.h"
+
 
 namespace gj {
 
@@ -18,11 +20,11 @@ public:
 
   virtual ~iAudioDevice() = default;
 
-  virtual void PlayMusic(const std::string& path, double offset) = 0;
-  virtual void StopMusic() = 0;
+  virtual void AddEffect(iAudioEffect* fx) = 0;
+  virtual void RemoveEffect(iAudioEffect* fx) = 0;
 
-  virtual void SetVolume(double amp) = 0;
-  virtual void SetLpfIntensity(double v) = 0;
+  virtual uint8_t  ch()         const = 0;
+  virtual uint32_t sampleRate() const = 0;
 };
 
 
diff --git a/src/iAudioEffect.h b/src/iAudioEffect.h
new file mode 100644
index 0000000..7f04b63
--- /dev/null
+++ b/src/iAudioEffect.h
@@ -0,0 +1,26 @@
+#pragma once
+
+#include <cstdint>
+
+
+namespace gj {
+
+
+/* Users have a responsible to remove AudioEffect from all devices at its destruction. */
+class iAudioEffect {
+ public:
+  iAudioEffect() = default;
+  iAudioEffect(iAudioEffect&&) = default;
+  iAudioEffect(const iAudioEffect&) = default;
+
+  iAudioEffect& operator=(iAudioEffect&&) = default;
+  iAudioEffect& operator=(const iAudioEffect&) = default;
+
+  virtual ~iAudioEffect() = default;
+
+  virtual void Apply(float* ptr, size_t frame) = 0;
+};
+
+
+
+}
\ No newline at end of file
diff --git a/src/iElement.h b/src/iElement.h
index 9cd6669..d8d0a3d 100644
--- a/src/iElement.h
+++ b/src/iElement.h
@@ -25,6 +25,8 @@ class iElement {
 
   virtual void Finalize() = 0;
 
+  virtual bool HasPrepared() const = 0;
+
   /* Interfaces had better not have a variable but this is for optimization. */
   const Period period;
 };