If you ever find yourself needing to translate a fox's various noises to English, here is a helpful guide of various vocalizations that he consistently makes, and what they seem to mean.
A throaty, three-or-five syllable call that roughly means "Someone come here!" He continues to call until someone in the family goes to where he is. It doesn't generally matter if it's a human, the dog, or one of the cats, so long as someone goes to him.
A high-pitched kit-like version of the same call that means "Ragtatter come here!" It is always three syllables, never five. If a different member of my family responds to him while doing this, he will continue to call until I specifically go in to see him. Thus far, I am the only member of the family that he uses a distinct "Come here!" call for.
A short "Awrf?" sort of noise that always ends higher-pitched than it starts. It seems to mean "What's that?" or "Look at that!" and is always accompanied by him staring at the object of his interest.
A lower-pitched "Awrrf!" that he uses whenever he sees a man in our house that is not my dad or brother, generally accompanied by him immediately finding something to pee on. His body language for this is usually very alert, but not aggressive. "Hey! Hey dude! This is my house! Just so you know."
A high-pitched whining, accompanied by ears laid back. Usually accompanied by him opening and closing his mouth as he whines, making an "Ar ar ar ar ar" sound. Generally this means "Someone is being mean to me!", though recently it almost always means "The kitty is teasing me!". He will sometimes hide his face while doing this (i.e. in my lap, down the neck of my shirt), which gives it more of a sobbing sound.
A high-pitched grumbling with a throatier sound to it. Generally this is heard during routine tasks that he dislikes (grooming, nails getting trimmed, baths, etc.) Back when I could walk him, he'd also start doing this when it was time to turn around and come home. Seems to mean "I don't like this!" or "I'm not happy."
A high-pitched warbling sort of noise; we've dubbed it a "Yarwarble". He uses this during play, and will often yarwarble and sink into a play-bow before pouncing or nomming or kicking with his hind legs. It seems to mean "I'm about to do something that might be misconstrued as aggression, but I'm just playing, so don't get scared or mad!"
High-pitched incoherent shrieking. This means "I'm not getting what I want and I'm mad as hell about it!" or "SOMEONE IS STEALING FROM ME!" Generally accompanied by flattened ears and pacing. He does this when dinner is late, or he's not allowed to steal something from the dog, or I won't take him outside when he wants to go outside, or I turn off the cartoons he was watching, or any other little situation where something is "taken away".
"Gekkering." Sort of a gurgling, rattling squawk. Always accompanied by a really intense foxy smell. He only does this when he is REALLY upset or REALLY scared. Not one I see very often, thankfully.
Squealing: Similar to the "Someone is stealing from me!" shriek, but the body language for this is completely different. Generally we hear this one when he gets a particularly good treat, or a new toy. He will pick up the object in his mouth, wag his whole body from his shoulders back, and just squeal at the top of his lungs. Probably means something along the lines of, "I'm so excited I just have to scream about it!"