Wow, that was a cool hint ... I don't have an SD-card connected, but in the sample there is also an "AudioOutputAnalog" Object. Inserting this object instead of the sgtl5000 makes it working! Just the Teensy, a USB-Cable, and my Computer.
Next step are the Touch Sense Pins ...
#include <Audio.h>
#include <Wire.h>
#include <SPI.h>
#include <SD.h>
#include <SerialFlash.h>
// GUItool: begin automatically generated code
AudioSynthKarplusStrong string1; //xy=183.1999969482422,164.1999969482422
AudioOutputAnalog dac; //xy=464.20001220703125,194.99998474121094
AudioOutputUSB usb1; //xy=467.1999969482422,120.19999694824219
AudioConnection patchCord2(string1, 0, usb1, 0);
AudioConnection patchCord3(string1, 0, usb1, 1);
// GUItool: end automatically generated code
void setup() {
// put your setup code here, to run once:
AudioMemory(15);
}
void loop() {
// put your main code here, to run repeatedly:
string1.noteOn(110.0, 1); delay(100);
string1.noteOn(130.8, 1); delay(100);
string1.noteOn(164.8, 1); delay(100);
string1.noteOn(220.0, 1); delay(500);
string1.noteOff(10); delay(1000);
}