Sure, I wrote code for a 13-note "piano" a while back using micros() and blink without delay style programming.
The notes were mixed together externally before going to the sound making device, in my case a powered PC speaker.
Code & schematic here.
https://forum.arduino.cc/index.php?topic=179761.0
Video of it here playing up to 8 notes, as that was all the buttons I had.
