Hi,
kaneshadow:
I'm curious what the limitation is
Timers. One tone per timer.
so that I can throw money at it by buying more components
Yes.
Is it because there is only 1 timer?
There are three timers on the Uno. One timer is used for millis, micros, delay, and delayMicroseconds. The other two timers can be used to generate tones. This will allow you to use more timers for generating tones...
http://code.google.com/p/rogue-code/wiki/ToneLibraryDocumentation
How would I fix that? Timer ICs?
http://arduino.cc/en/Main/ArduinoBoardMega
http://arduino.cc/en/Main/ArduinoBoardMega2560
https://www.google.com/search?hl=en&q=i2c+tone+generator
https://www.google.com/search?hl=en&q=spi+tone+generator