Playing two .wav at the same time

Hello everyone,
I would like to creat a drum pad so, I need to create differents buttons and play different wav file.
AudioFormatManager formatManager;
std::unique_ptr readerSource;
AudioTransportSource transportSource;

AudioFormatManager formatManager2;
std::unique_ptr readerSource2;
AudioTransportSource transportSource2;

But I had a problem only one on two works.
I think the problem is : getNextAudioBlock can be associated only with one transport source.