Is it possible (respectively is there a shield) to playback multiple audio-files simultaneously
No.
You can only open one file at a time on SD cards, and you can't read two SD cards fast enough. A wave shield is limited to 25KHz wav files anyway.
Is it possible (respectively is there a shield) to playback multiple audio-files simultaneously
No.
You can only open one file at a time on SD cards, and you can't read two SD cards fast enough. A wave shield is limited to 25KHz wav files anyway.