There's never a silly question.
Actually, that's a clever question. If you have two rMP3's stacked, using the same serial pins, you could send commands to both of them simultaneously. Works great (I even tested it out here). Just don't expect to get any meaningful data back from the rMP3s - they will both be vying for control of the Arduino receive pin.
Here's the code I used:
#include <RogueMP3.h>
#include <NewSoftSerial.h>
NewSoftSerial rmp3_s(6, 7);
RogueMP3 rmp3(rmp3_s);
void setup()
{
rmp3_s.begin(9600);
rmp3.sync();
rmp3.playfile("/ump3test.mp3");
}
void loop()
{
}
In theory, you could stack 10 rMP3's up on the Arduino, and send a single command to start them all at the same time. Have the same named file on each card play a separate instrument track from a symphony, and they would all play together. Of course, you'd need a 10 channel stereo mixer to mix all the outputs, but that's another story.
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