Code:

#include <Audio.h>
#include <Wire.h>
#include <SPI.h>
#include <SD.h>
#include <SerialFlash.h>
// GUItool: begin automatically generated code
AudioSynthWaveform osc1; //xy=75,80
AudioSynthWaveform osc2; //xy=75,120
AudioSynthWaveform osc3; //xy=75,160
AudioSynthNoiseWhite noise; //xy=75,200
AudioSynthWaveform fltOsc; //xy=75,300
AudioSynthWaveformDc fltDC; //xy=75,380
AudioEffectEnvelope fltDCEnv; //xy=226,420
AudioEffectEnvelope fltOscEnv; //xy=226.5,340
AudioMixer4 oscMx; //xy=255,140
AudioEffectEnvelope ampEnv; //xy=366,220
AudioMixer4 fltMx; //xy=438,340
AudioMixer4 ampMx; //xy=479,140
AudioFilterLadder ladder; //xy=622,140
AudioOutputI2S audioOut; //xy=793,141
AudioConnection patchCord1(osc1, 0, oscMx, 0);
AudioConnection patchCord2(osc2, 0, oscMx, 1);
AudioConnection patchCord3(osc3, 0, oscMx, 2);
AudioConnection patchCord4(noise, 0, oscMx, 3);
AudioConnection patchCord5(fltOsc, 0, fltMx, 0);
AudioConnection patchCord6(fltOsc, fltOscEnv);
AudioConnection patchCord7(fltDC, fltDCEnv);
AudioConnection patchCord8(fltDC, 0, fltMx, 2);
AudioConnection patchCord9(fltDCEnv, 0, fltMx, 3);
AudioConnection patchCord10(fltOscEnv, 0, fltMx, 1);
AudioConnection patchCord11(oscMx, 0, ampMx, 0);
AudioConnection patchCord12(oscMx, ampEnv);
AudioConnection patchCord13(ampEnv, 0, ampMx, 1);
AudioConnection patchCord14(fltMx, 0, ladder, 1);
AudioConnection patchCord15(ampMx, 0, ladder, 0);
AudioConnection patchCord16(ladder, 0, audioOut, 0);
AudioConnection patchCord17(ladder, 0, audioOut, 1);
// GUItool: end automatically generated code

Take particular note of the following: everywhere that an envelope is included, a mixer follows. These mixers allow you to select the "non-enveloped" signal (bypass the envelope) or the "enveloped" signal (apply the envelope). Using my best guess, you should be able to do any of the following: apply an envelope to the "fltOSC", apply a separate envelope to "fltDC", and use a mix of any of them, per your choosing.