Tone library and millis clash?

In the description of the Tone library, it states:-

" Also, although it's the last timer to be allocated, timer 0 (which is used for millis() among other things) will be affected if used. "

Does this mean only while the tone is playing? or will my timing of my project which uses the millis for a countdown timer be compromised by merely calling up the tone library?

I want to sound a horn at the end of the countdown, so I dont need the timer then.. I just need confirmation

How many tones will be playing at one time?

I think just one, I want to make a horn type sound for the end of a timeout period, a square wave into a fet amp and speaker. Not worried about distortion, just lots of noise ( that's what my late Dad used to say about the Beatles :-) )

Then you'll be fine.