diff --git a/src/sound.cpp b/src/sound.cpp
index 1951440..8e272d3 100644
--- a/src/sound.cpp
+++ b/src/sound.cpp
@@ -113,7 +113,9 @@ void Sound::play_task(void *pvParameter) {
 
   xTaskToNotify = xTaskGetCurrentTaskHandle();
 
-  File file = SDCard::open(path);
+//  Serial.print("before SDCard::open(); free stack: "); Serial.println(uxTaskGetStackHighWaterMark( NULL ), DEC); // DEBUG
+
+  File file = SDCard::open(path); // ToDo: accessing static member function loads 1500 words onto stack!
   if (!file) {
     xTaskToNotify = NULL;
     Serial.print("Failed to open file: "); Serial.println(path);
@@ -121,9 +123,11 @@ void Sound::play_task(void *pvParameter) {
     return;
   }
 
+//  Serial.print("before new; free stack: "); Serial.println(uxTaskGetStackHighWaterMark( NULL ), DEC); // DEBUG
   unsigned char* buf = new unsigned char[BUF_LENGTH];
   unsigned int buf_pos;
   Serial.print("Allocated buffer at: ");   Serial.println((int)buf,HEX);
+//  Serial.print("after new; free stack: "); Serial.println(uxTaskGetStackHighWaterMark( NULL ), DEC); // DEBUG
 
   i2s_start(i2s_num);
 
@@ -174,20 +178,3 @@ void Sound::play_task(void *pvParameter) {
   xSemaphoreGive( xPlayingSemaphore );
   vTaskDelete( NULL );
 }
-
-/* callback(?) for new audio data */
-int Sound::render_sample_block(uint16_t *sample_buf_left, uint16_t *sample_buf_right, int num_samples) {
-  TickType_t delay = 10 / portTICK_PERIOD_MS; // max delay: 10ms instead of portMAX_DELAY
-  int num_pushed_samples = 0;
-  for (int i=0; i < num_samples; i++) {
-    unsigned int sample = ((unsigned short) sample_buf_left[i] << 16 & 0xffff0000) | ((unsigned short) sample_buf_right[i]);
-    int num_pushed_bytes = i2s_push_sample(i2s_num, (char *)&sample, delay);
-    if (num_pushed_bytes > 0) {
-      num_pushed_samples += num_pushed_bytes;
-    } else {
-      Serial.println("i2s buffer filled");
-      break;
-    }
-  }
-  return num_pushed_samples;
-}
diff --git a/src/sound.h b/src/sound.h
index 9502330..b383776 100644
--- a/src/sound.h
+++ b/src/sound.h
@@ -16,7 +16,6 @@ class Sound {
     void play(const char*);
 //    void pause();
 //    void stop();
-    int render_sample_block(uint16_t *sample_buf_left, uint16_t *sample_buf_right, int num_samples);
     static const i2s_port_t i2s_num = (i2s_port_t)I2S_NUM;
     static void play_task(void *pvParameter);
   private: