Processor Scheduling

Having trouble scheduling the processor to perform two long running tasks. I could simplify this to using the second core, but I am trying to achieve it using a single core chip in the end. If anyone has any good resources for mcu scheduling please share.

My project involves an NEC Infrared remote, and the main loop is generally waiting for a signal from the controller to know what it should be doing. I have a couple process that are automated and should be long running, using a second thread solves this problem easy, but trying to do something like spin a motor while waiting for infrared pulses is seeming very complicated for me. I understand I should be using the time between work to do other work, ie spin the motor, check for a pulse, then spin the motor again, but this does not give great control over a remote control. How would a simple product like an mp3 player or a drone function, playing music or spinning propellers while waiting for commands from the master?