I've been thinking about this a lot lately, it's more of an opinion question. When does a bunch of chords and notes just become sound instead of music? when there is no time signature or key or even a root chord to follow, is it just noise? or is it an interpretation of a situation or thought? where is the line between noise and music? is there a line? is a song that is just 16th notes in 15/16 time randomly and chromatically played music? or even.... The "A" word, art? I hope you have an opinion on this, thanks.

It's music when I write it. When someone else writes it, it's just noise. ;)

Seriously though, I think music is 90% culture and 10% mathematics. Generally I think music arises by combining sounds in an arbitrarily structured way, and you can therefore only judge something's music-like qualities by being aware of the structures you intend to judge it by, which vary from place to place, and to a lesser degree, from person to person.

At the extreme reverse end of the scale you've got John Cage's 4:33. It contains no chords or notes whatsoever. Is it music?

You'll argue for years on the philosophical side of this question and not get anywhere. Practically, I'd say that some of the dungeon "songs" in Ocarina of Time, for example, didn't really qualify as music. They were notes, and they were even strung together in patterns, but they didn't really have any kind of musical "plot", so to speak (I'm not up on my musical terminology); they were just a set of patterns strung together. They provided atmosphere and mood, but that was about all.

It's an interesting question and one that I feel doesn't have an answer. The concept of 'music' isn't a static physical thing that can be easily identified. Similarly, when does something become 'art'? The best answer I can think of for that is that it is art when you put it in a large white room and put a plaque with some writing on next to it ;D

I am a sound designer and much of my work ventures into 'music' territory and I find it difficult to know when that line is crossed sometimes. But to directly answer, I guess sound design is something that affects more physical responses such as 'cold', 'islotated', 'busy', etc where music affects more emotive responses like 'sadness'. I feel music taps into more complex emotions and themes but sound design is more primal and less open to misinterpretation.

Music is just a word, one that was created at a time when it was easier to define. A composer can make a song that is primarily noise based without much in the sense of a defined rhythm and a sound designer can create a sound that is highly rythmical and has very pronounced frequencies and harmonics, so there is a lot of cross pollination.

But for me, I know that I'm happier being a sound designer :)

Unfortunately, I think a lot of people would say that it comes down to what the composer decides it is. If John Cage calls 4'33" music, it is music--the aleatoric quality of the audience sounds and all that is the whole point of the piece. I think it's close to that, though; what it comes down to is "decision:" if you feed instructions to a computer to generate random tones, and nobody made any decisions about what the parameters are, then I think that's not music, regardless of what the composer says. If you put sounds together with the intent of calling it music, then it is music--it's an unfortunately broad standard, but I think that's where it has to come to rest.
Some "ambient" scores have almost no identifiable sense of rhythm or pitch, but someone put it together with the intent of specific sounds coming together to form a certain mood that they label music. It may not be GOOD music, but it's music nonetheless, since it was composed to be music; which I'm sure is what Beethoven would say about say, Creed. To his ears, it's just noise (and I'm not that far removed from his opinion); conversely, I've heard it said by a native of India that Western music is boring and not that rhythmically interesting (this was a commentary on Beethoven's 5th!). So it all has to do with your ears and what the composer's intent is.

How many people would identify 4:33 as a piece of music without a concert hall and a program? I find it interesting that the only people who would classify this as music as opposed to some sort of performance art seem to be other musical academics, and there is even a wide range of disagreement inside of that group. If random noises in a hall become music then whats to stop a police siren from being a symphony and a gassy dog from being a concertist?

It reminds me of what that senator had to say a few years back when he was asked "what is pornography?" and he replied "I can't define it, but I know it when I see it." After studying music for almost ten years, I can't objectively define it, but I definitely know what it isn't.

Go listen to screamo rock like Hawthorne Heights and you'll find out. Although I think noise is a bit more accurate term than sound.

Louis Armstrong once said that if you can tap your foot to a song, it's good music. could this be a good standard to use?

I'd say that's sufficient, but not necessary. For example, most opera is not foot-tappable. A large part of the value of music is the degree to which you can get the audience to invest themselves in the piece; like any art, the goal of music is to affect the listener. The problem here is that ambient sounds can affect the listener as well - most horror games use this to good effect, for example - and you need something to differentiate the two. I guess perhaps the difference would be between the listener investing himself in the piece itself, or in the atmosphere it creates. Simple creaking floorboards don't do much on their own; it's the combination of the creaking with the dark, deserted, and unfamiliar house that create the mood. In contrast, music is able to affect you on its own; context can help but is not required.