This is a classic state-machine problem. That isn't the only way to do it but it's just made for this kind of problem, one in which only certain external events are interesting at a given time; and when such an event occurs, the controller must tweak the outside world in some way, and then start paying attention to a different set of interesting events.

Does playing a sound file totally occupy the Arduino until the sound is done? And if so, can your process tolerate the controller being unresponsive for the duration of the sound track? Because otherwise you'll need something more capable than an Arduino, or you'll need to be able to program the Arduino to feed the sound in small pieces to a buffered sound card, so it (the Arduino) can continue monitoring the interesting set of possible events while the sound is playing. That probably means some clever programming with the SimpleTimer library or similar, or using interrupt service routines to inform some part of your code when an event occurs. Probably the ideal cases would be to have a "sound machine" that can play 'n' different tracks, and would do so autonomously when told to start playing track 'j'. Begins to sound like another MCU just handling sound, doesn't it?

Update:

Look up state machine diagrams - basically circles representing states and arrows representing transitions to a new state in response to an events. There are several ways to put the state machine's control of the external equipment; my choice is that each state "does something" then "waits for something to happen", where something to happen may include a clock signal indicating the event(s) it was waiting for didn't happen (i.e. a timeout). Look at some state diagrams to get an idea how they are used, then start diagramming your own project.

I draw the "happy path" straight down the page - that path that represent normal or expected operation - with less usual or error paths drawn to either side. At that point you should be pretty confident in your algorithm.

There are several ways to code state machines - that'll be a further discussion.

This is a classic state-machine problem. That isn't the only way to do it but it's just made for this kind of problem, one in which only certain external events are interesting at a given time; and when such an event occurs, the controller must tweak the outside world in some way, and then start paying attention to a different set of interesting events.

Does playing a sound file totally occupy the Arduino until the sound is done? And if so, can your process tolerate the controller being unresponsive for the duration of the sound track? Because otherwise you'll need something more capable than an Arduino, or you'll need to be able to program the Arduino to feed the sound in small pieces to a buffered sound card, so it (the Arduino) can continue monitoring the interesting set of possible events while the sound is playing. That probably means some clever programming with the SimpleTimer library or similar, or using interrupt service routines to inform some part of your code when an event occurs. Probably the ideal cases would be to have a "sound machine" that can play 'n' different tracks, and would do so autonomously when told to start playing track 'j'. Begins to sound like another MCU just handling sound, doesn't it?

Update:

Look up state machine diagrams - basically circles representing states and arrows representing transitions to a new state in response to an events. There are several ways to put the state machine's control of the external equipment; my choice is that each state "does something" then "waits for something to happen", where something to happen may include a clock signal indicating the event(s) it was waiting for didn't happen (i.e. a timeout). Look at some state diagrams to get an idea how they are used, then start diagramming your own project.

I draw the "happy path" straight down the page - that path that represents the normal or expected operation - with less usual or error paths drawn to either side. At that point you should be pretty confident in your algorithm.

There are several ways to code state machines - that'll be a further discussion.

This is a classic state-machine problem. That isn't the only way to do it but it's just made for this kind of problem, one in which only certain external events are interesting at a given time; and when such an event occurs, the controller must tweak the outside world in some way, and then start paying attention to a different set of interesting events.

Does playing a sound file totally occupy the Arduino until the sound is done? And if so, can your process tolerate the controller being unresponsive for the duration of the sound track? Because otherwise you'll need something more capable than an Arduino, or you'll need to be able to program the Arduino to feed the sound in small pieces to a buffered sound card, so it (the Arduino) can continue monitoring the interesting set of possible events while the sound is playing. That probably means some clever programming with the SimpleTimer library or similar, or using interrupt service routines to inform some part of your code when an event occurs. Probably the ideal cases would be to have a "sound machine" that can play 'n' different tracks, and would do so autonomously when told to start playing track 'j'. Begins to sound like another MCU just handling sound, doesn't it?

This is a classic state-machine problem. That isn't the only way to do it but it's just made for this kind of problem, one in which only certain external events are interesting at a given time; and when such an event occurs, the controller must tweak the outside world in some way, and then start paying attention to a different set of interesting events.

Does playing a sound file totally occupy the Arduino until the sound is done? And if so, can your process tolerate the controller being unresponsive for the duration of the sound track? Because otherwise you'll need something more capable than an Arduino, or you'll need to be able to program the Arduino to feed the sound in small pieces to a buffered sound card, so it (the Arduino) can continue monitoring the interesting set of possible events while the sound is playing. That probably means some clever programming with the SimpleTimer library or similar, or using interrupt service routines to inform some part of your code when an event occurs. Probably the ideal cases would be to have a "sound machine" that can play 'n' different tracks, and would do so autonomously when told to start playing track 'j'. Begins to sound like another MCU just handling sound, doesn't it?

Update:

Look up state machine diagrams - basically circles representing states and arrows representing transitions to a new state in response to an events. There are several ways to put the state machine's control of the external equipment; my choice is that each state "does something" then "waits for something to happen", where something to happen may include a clock signal indicating the event(s) it was waiting for didn't happen (i.e. a timeout). Look at some state diagrams to get an idea how they are used, then start diagramming your own project.

I draw the "happy path" straight down the page - that path that represent normal or expected operation - with less usual or error paths drawn to either side. At that point you should be pretty confident in your algorithm.

There are several ways to code state machines - that'll be a further discussion.