Looks like I just ran into the same problem with the Teensy 1.45 release - the SoundFontDecoder.exe program doesn't seem to add the required "AudioSynthWavetable::" to the generated .cpp/.h files
I guess that hasn't been updated to match the Python source files yet?
I'm having a similar problem with SD1106/SD1306 OLED displays and Teensy3.6 specifically.
The code is Ornaments and Crimes ( https://github.com/mxmxmx/O_C/tree/master/software/o_c_REV )
I'm using the Alternate SPI pins (SCK=D14, MISO=D12, MOSI=D7) and I change them using -...
Sounds like the SGTL5000 is a better choice for Quad outputs right now.
Or just go for a native TDM part for more channels, like the Cirrus CS42448,
since that is already supported.
thanks again, Tom