Examples need #include <SoftwareSerial.h> if you are not useng hardware

[bhelterline]

The examples show using HardwareSerial with commented out SoftwareSerial alternative. You should also have commented out the line to include the library since it is needed.

They should contain this:

// Some arduino boards only have one hardware serial port, so a software serial port is needed instead.
// comment out the above definitions and use these
//#include <SoftwareSerial.h>
//SoftwareSerial secondarySerial(10, 11); // RX, TX
//typedef DFMiniMp3<SoftwareSerial, Mp3Notify> DfMp3;
// DfMp3 dfmp3(secondarySerial);

This is needed for all the examples