Interval Timer Library used with tone function

[BLMinTenn]

All,
First of all Good Afternoon.

Second, I have a few questions about the 4 PIT "timers" for the Teensy 3.2 only for the sake of learning.

Here goes. I have been reading the kinetis.h file and the K10 reference manual about timers 0 thru 3. So, looking in the IntervalTimer.cpp under the function beginCycles(), I see the following...

if (channel) {
     channel->TCTRL = 0;
     channel->TFLG = 1;}

In the if statement I assume that "channel" is being treated as 1 thru 3 as true and 0 as false.

With that said, my question #1 is.... are only PIT timers 1-3 available to be used for IntervalTimer?
Question #2, Is the If statement resetting the Timer Control Register and telling the Timer Flag Register that time has exceded only for the timer that was previously used?

I do appreciate the clarification on this matter.

Thanks
BLMinTenn