Every command that is sent will take priority over background commands. Having a microcontroller play tones takes a lot of processing because it has limitted i/o functionality (at least without dedicated DAC hardware).

So in short, playing tones will consume the EZ-B's processor for each note.

Here is a great suggestion, however. If your robot requirement is to have many interactive tones, then a $40 USD wireless hub (available through parallax) may be an option. This will allow you to use a very inexpensive USB soundcard and play Digital and Wave media.

The next version of ARC contains MIDI, WAV and MP3 functionality.

Due to the low cost of the wireless USB Hub, the ARC will contain many functions to support USB hardware in the future. :)

Thanks for the reply I understand why this is happening now

Great suggestion with the wireless hub and incorporating that with ARC

Thanks