Yes as mentioned the ADC library works great for this.
I have a WIP (Need to get back to it) Well monitor program, that uses 4 Analog sensors (actually current sensors), that I read. Two at a time, with none of them holding up the CPU while they do their work.
I have the 4 setup such that two are on ADC0 and two on ADC1 (T3.6).
I have code called on an Interval timer that completes the analog read of two sensors and starts the read of the other two, which will be read on next interval timer.
You start the read using something like: adc->startSingleRead(_pin, _adc_num)
You can test to see if the read is done: adc->isComplete(_adc_num)
Read in the results: adc->readSingle(_adc_num)
Again the latest stuff is up at:
https://github.com/pedvide/ADC
My guess it currents the same as the version that downloads with Teensyduino