diff --git a/sampler/platformio.ini b/sampler/platformio.ini
index 3e51ed2..0d45977 100644
--- a/sampler/platformio.ini
+++ b/sampler/platformio.ini
@@ -14,44 +14,19 @@ default_envs = teensy35
 [common]
 lib_ignore = Audio, SD
 lib_deps =
-  721 ; TaskScheduler
-  322 ; SdFat
-  401 ; Adafruit SleepyDog Library
+  721@3.0.2 ; TaskScheduler
+  322@1.0.7 ; SdFat
 
 [env:teensy35]
-platform = teensy
+platform = teensy@3.6.0
 board = teensy35
 framework = arduino
 lib_deps = ${common.lib_deps}
 lib_ignore = ${common.lib_ignore}
 
 [env:teensy36]
-platform = teensy
+platform = teensy@3.6.0
 board = teensy36
 framework = arduino
 lib_deps = ${common.lib_deps}
 lib_ignore = ${common.lib_ignore}
-
-
-; [platformio]
-; env_default = teensy35
-;
-; [common]
-; lib_ignore = Audio, SD
-; lib_deps =
-;   721@3.0.2 ; TaskScheduler
-;   322@1.0.7 ; SdFat
-;
-; [env:teensy35]
-; platform = teensy@3.6.0
-; board = teensy35
-; framework = arduino
-; lib_deps = ${common.lib_deps}
-; lib_ignore = ${common.lib_ignore}
-;
-; [env:teensy36]
-; platform = teensy@3.6.0
-; board = teensy36
-; framework = arduino
-; lib_deps = ${common.lib_deps}
-; lib_ignore = ${common.lib_ignore}
diff --git a/sampler/src/main.cpp b/sampler/src/main.cpp
index 33cb76c..7f0dc1a 100644
--- a/sampler/src/main.cpp
+++ b/sampler/src/main.cpp
@@ -16,33 +16,14 @@
 // (part-3) teensy35 : 'client:sampler' (mesh post --> play sounds)
 //
 
-//
-// 2019 12 29
-//
-// multiple sound playback -> 4 voices -- TESTING
-//
-
-//----------<configuration>----------
-//
-// 'ANALOG_REF_EXTERNAL_3P3V'
-// --> this will output 3.3v-pp from dacs pins of the board.
-//     outdoor or big space. you will need this.
-//     but, teensy36 board dacs pins once might have burned off cause of this?
-//     teensy35 was okay since they are stronger (5V compatible I/O)
-//
-// #define ANALOG_REF_EXTERNAL_3P3V
-//
-// 'LED_INDICATOR'
-// --> this will enable red LED on/off according to the file playback status.
-//
-#define LED_INDICATOR
-//----------</configuration>----------
-
-//watchdog
-#include <Adafruit_SleepyDog.h>
+//HACK: let auto-poweroff speakers stay turned ON! - (creative muvo mini)
+#define IDLE_FREQ 22000
+#define IDLE_AMP 0 // --> creative muvo 2 doesn't need this. they just stay on!
 
 //teensy audio
 #include <Audio.h>
+// #include <SPI.h>
+// #include <SD.h>
 #include <SdFat.h>
 SdFatSdioEX SD;
 #include <SerialFlash.h>
@@ -53,285 +34,98 @@ SdFatSdioEX SD;
 #define SDCARD_SCK_PIN   13  // not actually used
 
 // GUItool: begin automatically generated code
-AudioPlaySdWav playSdWav1;               //xy=183,90
-AudioPlaySdWav playSdWav2;               //xy=185,253
-AudioPlaySdWav playSdWav3;           //xy=187,411
-AudioPlaySdWav playSdWav4;           //xy=188,579
-AudioAmplifier amp1;                     //xy=374,49
-AudioAmplifier amp2;                     //xy=375,132
-AudioAmplifier amp3;           //xy=377,219
-AudioAmplifier amp4;           //xy=378,302
-AudioAmplifier amp5;           //xy=378,370
-AudioAmplifier amp6;           //xy=379,453
-AudioAmplifier amp7;           //xy=381,540
-AudioAmplifier amp8;           //xy=382,623
-AudioMixer4 mixer2;                      //xy=620,413
-AudioMixer4 mixer1;                      //xy=621,210
-AudioOutputAnalogStereo dacs1;           //xy=812,318
-AudioConnection patchCord1(playSdWav1, 0, amp1, 0);
-AudioConnection patchCord2(playSdWav1, 1, amp2, 0);
-AudioConnection patchCord3(playSdWav2, 0, amp3, 0);
-AudioConnection patchCord4(playSdWav2, 1, amp4, 0);
-AudioConnection patchCord5(playSdWav3, 0, amp5, 0);
-AudioConnection patchCord6(playSdWav3, 1, amp6, 0);
-AudioConnection patchCord7(playSdWav4, 0, amp7, 0);
-AudioConnection patchCord8(playSdWav4, 1, amp8, 0);
-AudioConnection patchCord9(amp1, 0, mixer1, 0);
-AudioConnection patchCord10(amp2, 0, mixer2, 0);
-AudioConnection patchCord11(amp3, 0, mixer1, 1);
-AudioConnection patchCord12(amp4, 0, mixer2, 1);
-AudioConnection patchCord13(amp5, 0, mixer1, 2);
-AudioConnection patchCord14(amp6, 0, mixer2, 2);
-AudioConnection patchCord15(amp7, 0, mixer1, 3);
-AudioConnection patchCord16(amp8, 0, mixer2, 3);
-AudioConnection patchCord17(mixer2, 0, dacs1, 1);
-AudioConnection patchCord18(mixer1, 0, dacs1, 0);
+AudioPlaySdWav playSdWav1;               //xy=224,265
+AudioSynthWaveformSine sine1;            //xy=236,361
+AudioMixer4 mixer2;                      //xy=497,328
+AudioMixer4 mixer1;                      //xy=499,245
+AudioAmplifier amp1;                     //xy=633,245
+AudioAmplifier amp2;                     //xy=634,328
+AudioOutputAnalogStereo dacs1;           //xy=788,284
+AudioConnection patchCord1(playSdWav1, 0, mixer1, 0);
+AudioConnection patchCord2(playSdWav1, 1, mixer2, 0);
+AudioConnection patchCord3(sine1, 0, mixer1, 1);
+AudioConnection patchCord4(sine1, 0, mixer2, 1);
+AudioConnection patchCord5(mixer2, amp2);
+AudioConnection patchCord6(mixer1, amp1);
+AudioConnection patchCord7(amp1, 0, dacs1, 0);
+AudioConnection patchCord8(amp2, 0, dacs1, 1);
 // GUItool: end automatically generated code
 
-//
-class Voice {
-  //private
-
-  //teensy audio
-  AudioPlaySdWav& player;
-  AudioAmplifier& ampL;
-  AudioAmplifier& ampR;
-
-  // a filename buffer
-  char filename[13];
-
-public:
-
-  //
-  int note_now;
-  int velocity_now;
-
-  //
-  Voice(AudioPlaySdWav& player_, AudioAmplifier& ampL_, AudioAmplifier& ampR_)
-    : player(player_)
-    , ampL(ampL_)
-    , ampR(ampR_)
-  {
-    //initializations
-    note_now = 0;
-    velocity_now = 0;
-    strcpy(filename, "NNN.WAV");
-  }
-
-  //
-  void noteOn(int note) {
-    // present my 'note' -> 'occupied'.
-    note_now = note;
-    // set filename to play...
-    int nnn = (note % 1000);  // 0~999
-    int nn =  (note % 100);   // 0~99
-    filename[0] = '0' + (nnn / 100); // N__.WAV
-    filename[1] = '0' + (nn / 10);   // _N_.WAV
-    filename[2] = '0' + (nn % 10);   // __N.WAV
-    // the filename to play is...
-    Serial.println(filename);
-    // go! (re-triggering)
-    // if (player.isPlaying()) player.stop();
-    player.play(filename);
-    // --> we just believe that this 'file' is existing & available. NO additional checking.
-    delay(10);
-    // --> let's wait a bit before exit, to give more room to work for background workers(==filesystem|audio-interrupts)
-    // --> if we get too fast 'player.play' twice, then the system might get broken/stalled. ?
-  }
-  //
-  void noteOff() {
-    player.stop();
-    delay(10); // wait to close file?
-    // present my 'note' -> 'free'.
-    note_now = 0;
-  }
-  //
-  void setVelocity(int val) {
-    if (val < 0) val = 0;
-    float vv = (float)val / 127; // allowing +gain for values over 127.
-    ampL.gain(vv);
-    ampR.gain(vv);
-  }
-  //
-  bool isPlaying() {
-    return player.isPlaying();
-  }
-};
-
-// voice banks
-#include <vector>
-#include <deque>
-static Voice __voice_1(playSdWav1, amp1, amp2);
-static Voice __voice_2(playSdWav2, amp3, amp4);
-static Voice __voice_3(playSdWav3, amp5, amp6);
-static Voice __voice_4(playSdWav4, amp7, amp8);
-static std::vector<Voice> poly_bank;
-static std::deque< std::pair<int, int> > poly_queue;
-
 //task
 #include <TaskScheduler.h>
 Scheduler runner;
-// polyphonics
-static int note_sched = 0;
-static int velocity_sched = 0;
-void scheduleNoteOn()
+//sample #
+int sample_now = 0; //0~99
+void sample_player_start()
 {
   //filename buffer - 8.3 naming convension! 8+1+3+1 = 13
-  char fname[13] = "NNN.WAV";
+  char filename[13] = "NNN.WAV";
   //search for the sound file
-  int note = note_sched;
+  int note = sample_now;
   int nnn = (note % 1000);  // 0~999
   int nn =  (note % 100);   // 0~99
-  fname[0] = '0' + (nnn / 100); // N__.WAV
-  fname[1] = '0' + (nn / 10);   // _N_.WAV
-  fname[2] = '0' + (nn % 10);   // __N.WAV
+  filename[0] = '0' + (nnn / 100); // N__.WAV
+  filename[1] = '0' + (nn / 10);   // _N_.WAV
+  filename[2] = '0' + (nn % 10);   // __N.WAV
   //TEST
-  Serial.println(fname);
+  Serial.println(filename);
   AudioNoInterrupts();
-  bool test = SD.exists(fname);
+  bool test = SD.exists(filename);
   AudioInterrupts();
   if (!test) {
     Serial.println("... does not exist.");
     return;
   }
-  //ok, let's schedule a voice
-  //btw, is it already playing?
-  // --> entry : (# of voice bank, playing note #)
-  bool is_already = false;
-  for (uint32_t idx = 0; idx < poly_queue.size(); idx++) {
-    if (poly_queue[idx].second == note) {
-      //oh, it is alreay playing
-      // --> what to do?
-      // (1) re-trigger (stop-and-restart)
-      // is_already = true;
-      // Voice& v = poly_bank[poly_queue[idx].first];
-      // v.noteOff();
-      // v.noteOn(note);
-      // v.setVelocity(velocity_sched);
-      // break;
-      // (2) do nothing (just let it play till end)
-      // is_already = true;
-      // break;
-      // (3) trigger a new one? (schedule a new one overlapping)
-      // --> then you just ignore the fact.
-      //     i.e. do not tick 'is_already = true',
-      //     then a new one will be automatically assigned.
-      break;
-    }
-  }
-  //it's sth. new..
-  if (is_already == false) {
-    //fine, is there idle voice?
-    bool is_found_idle = false;
-    for (uint32_t idx = 0; idx < poly_bank.size(); idx++) {
-      if (poly_bank[idx].note_now == 0) {
-        //cool, got one.
-        is_found_idle = true;
-        //play start-up
-        Voice& v = poly_bank[idx];
-        v.noteOn(note);
-        v.setVelocity(velocity_sched);
-        //leave a record : (# of voice bank, playing note #)
-        poly_queue.push_back(std::pair<int, int>(idx, note));
-        break;
-      }
-    }
-    //oh, no idle one!
-    if (is_found_idle == false) {
-      //then, who's the oldest?
-      int oldest = poly_queue.front().first;
-      poly_bank[oldest].noteOff();
-      poly_queue.pop_front();
-      //
-      int newentry = oldest;
-      //
-      Voice& v = poly_bank[newentry];
-      v.noteOn(note);
-      v.setVelocity(velocity_sched);
-      //leave a record : (# of voice bank, playing note #)
-      poly_queue.push_back(std::pair<int, int>(newentry, note));
-    }
-  }
-  //small waiting time for 'isPlaying' update?
-  // delay(10);
-  //monitoring the queue
-  Serial.println("--notoOn:poly_queue---");
-  Serial.println("(voice#, note#)");
-  for (uint32_t idx = 0; idx < poly_queue.size(); idx++) {
-    Serial.print("(");
-    Serial.print(poly_queue[idx].first);
-    Serial.print(", ");
-    Serial.print(poly_queue[idx].second);
-    Serial.println(")");
-  }
-  Serial.println();
+  //start the player!
+  //NOTE: block out 're-triggering'
+  // if (playSdWav1.isPlaying() == false) {
+  playSdWav1.play(filename);
+  // }
+  //mark the indicator : HIGH: ON
+  digitalWrite(13, HIGH);
+  //to wait a bit for updating isPlaying()
+  delay(10);
 }
-//
-Task scheduleNoteOn_task(0, TASK_ONCE, scheduleNoteOn);
-//
-void scheduleNoteOff() {
-  for (auto it = poly_queue.begin(); it != poly_queue.end(); ++it) {
-    //is this meaningful, btw?
-    if ((*it).second == note_sched) {
-      //okay. we've got that.
-      Serial.println("okay. we've got that.");
-      //a record : (# of voice bank, playing note #)
-      poly_bank[(*it).first].noteOff(); // stop the bank
-      poly_queue.erase(it); // remove the record
-      break;
-    }
+void sample_player_stop() {
+  //filename buffer - 8.3 naming convension! 8+1+3+1 = 13
+  char filename[13] = "NNN.WAV";
+  //search for the sound file
+  int note = sample_now;
+  int nnn = (note % 1000);  // 0~999
+  int nn =  (note % 100);   // 0~99
+  filename[0] = '0' + (nnn / 100); // N__.WAV
+  filename[1] = '0' + (nn / 10);   // _N_.WAV
+  filename[2] = '0' + (nn % 10);   // __N.WAV
+  //TEST
+  Serial.println(filename);
+  AudioNoInterrupts();
+  bool test = SD.exists(filename);
+  AudioInterrupts();
+  if (!test) {
+    Serial.println("... does not exist.");
+    return;
   }
-  //monitoring the queue
-  Serial.println("--notoOff:poly_queue---");
-  Serial.println("(voice#, note#)");
-  for (uint32_t idx = 0; idx < poly_queue.size(); idx++) {
-    Serial.print("(");
-    Serial.print(poly_queue[idx].first);
-    Serial.print(", ");
-    Serial.print(poly_queue[idx].second);
-    Serial.println(")");
+  //stop the player.
+  if (playSdWav1.isPlaying() == true) {
+    playSdWav1.stop();
   }
-  Serial.println();
 }
-//
-Task scheduleNoteOff_task(0, TASK_ONCE, scheduleNoteOff);
-
-//
-extern Task playcheck_task;
-void playcheck() {
-  //
-  if (playcheck_task.isFirstIteration()) {
-    //watchdog
-    Watchdog.enable(1000);
-  }
-  //
-#if defined(LED_INDICATOR)
-  //
-  bool is_nosound = true;
-  for (uint32_t idx = 0; idx < poly_bank.size(); idx++) {
-    if (poly_bank[idx].isPlaying()) {
-      is_nosound = false;
-    }
-  }
-  if (is_nosound) {
+void sample_player_check() {
+  if (playSdWav1.isPlaying() == false) {
     //mark the indicator : LOW: OFF
     digitalWrite(13, LOW);
-  } else {
-    //mark the indicator : HIGH: ON
-    digitalWrite(13, HIGH);
+    //let speaker leave turned ON!
+    sine1.amplitude(IDLE_AMP);
+  }
+  else {
+    //let speaker leave turned ON!
+    sine1.amplitude(0);
   }
-#endif
-
-  // //
-  // Serial.print("AM_max:");
-  // Serial.println(AudioMemoryUsageMax());
-
-  //watchdog
-  Watchdog.reset();
-  // Serial.println("Watchdog.reset");
 }
 //
-Task playcheck_task(200, TASK_FOREVER, playcheck);
+Task sample_player_start_task(0, TASK_ONCE, sample_player_start);
+Task sample_player_stop_task(0, TASK_ONCE, sample_player_stop);
+Task sample_player_check_task(0, TASK_FOREVER, sample_player_check, &runner, true);
 
 //i2c
 #include <Wire.h>
@@ -377,17 +171,20 @@ void receiveEvent(int numBytes) {
 
     //
     int key = str_key.toInt();
-    int velocity = str_velocity.toInt(); // 0 ~ 127
-    int gate = str_gate.toInt();
-
+    sample_now = key;
     //
+    int velocity = str_velocity.toInt(); // 0 ~ 127
+    float amp_gain = (float)velocity / 127.0;
+    amp1.gain(amp_gain);
+    amp2.gain(amp_gain);
+    //
+    int gate = str_gate.toInt();
     if (gate == 0) {
-      note_sched = key;
-      scheduleNoteOff_task.restart();
+      sample_player_stop_task.restart();
+      Serial.println("sample_player_stop_task");
     } else {
-      note_sched = key;
-      velocity_sched = velocity;
-      scheduleNoteOn_task.restart();
+      sample_player_start_task.restart();
+      Serial.println("sample_player_start_task");
     }
   }
 }
@@ -439,8 +236,10 @@ void setup() {
   // DISABLED.. due to bi-directional I2C hardship. ==> use UART.
   // Wire.onRequest(requestEvent);
 
-  //SD
+  //SD - AudioPlaySdWav @ teensy audio library needs SD.begin() first. don't forget/ignore!
+  //+ let's additionally check contents of SD.
   if (!SD.begin()) {
+    // if (!SD.begin(BUILTIN_SDCARD)) {
     Serial.println("[sd] initialization failed!");
     return;
   }
@@ -448,51 +247,34 @@ void setup() {
   root = SD.open("/");
   printDirectory(root, 0);
 
-  //polyphonics - 4 voices
-  poly_bank.push_back(__voice_1);
-  poly_bank.push_back(__voice_2);
-  poly_bank.push_back(__voice_3);
-  poly_bank.push_back(__voice_4);
-
   //audio
-  AudioMemory(20); // <-- used AudioMemoryUsageMax() to check out!
+  AudioMemory(20);
 #if !defined(TEENSY36)
-  //NOTE!! teensy36 board..
-  //       output broken? ..
-  //       so disable this for teensy36..
-  //       this is the cause??
-#if defined(ANALOG_REF_EXTERNAL_3P3V)
+  //NOTE!! teensy36 board.. output broken? .. so disable this for teensy36.. this is the cause??
   dacs1.analogReference(EXTERNAL);
-#endif
 #endif
   mixer1.gain(0,1.0);
   mixer1.gain(1,1.0);
-  mixer1.gain(2,1.0);
-  mixer1.gain(3,1.0);
+  mixer1.gain(2,0);
+  mixer1.gain(3,0);
   mixer2.gain(0,1.0);
   mixer2.gain(1,1.0);
-  mixer2.gain(2,1.0);
-  mixer2.gain(3,1.0);
+  mixer2.gain(2,0);
+  mixer2.gain(3,0);
   amp1.gain(1.0);
   amp2.gain(1.0);
-  amp3.gain(1.0);
-  amp4.gain(1.0);
-  amp5.gain(1.0);
-  amp6.gain(1.0);
-  amp7.gain(1.0);
-  amp8.gain(1.0);
 
-  //tasks
-  runner.addTask(playcheck_task);
-  playcheck_task.restartDelayed(60000); // watchdog start after 60 sec. waiting task scheduling system stabilizing takes that so much time!
-  //
-  runner.addTask(scheduleNoteOn_task);
-  runner.addTask(scheduleNoteOff_task);
+  //let auto-poweroff speakers stay turned ON!
+  sine1.frequency(IDLE_FREQ);
 
   //led
   pinMode(13, OUTPUT);
   digitalWrite(13, LOW); // LOW: OFF
 
+  //player task
+  runner.addTask(sample_player_start_task);
+  runner.addTask(sample_player_stop_task);
+
   //
   Serial.println("[setup] done.");
 }
diff --git a/src/main.cpp b/src/main.cpp
index 6edb1c0..cd587f8 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -64,7 +64,7 @@
 
 //==========<preset>===========
 // (1) the backbone AP
-#if 1
+#if 0
 #define DISABLE_I2C_REQ
 #define SET_CONTAINSROOT
 // (2) osc client (the ROOT)
@@ -72,7 +72,7 @@
 #define SET_ROOT
 #define SET_CONTAINSROOT
 // (3) sampler client
-#elif 0
+#elif 1
 #define DISABLE_AP
 #define DISABLE_I2C_REQ
 //