I got an album by Ornette Coleman and Pat Metheny, "X", and on the linear notes it talks about atonal experiments within the song structures. Are there scales and chord progressions that go along with atonal music?
Yes there are scales and chords! You can have chords in atonal music. You simply cannot have a "key". A Key is a hierarchy of notes where some notes are more important that others. In atonality your goal is to have all notes equal(which is impossible to do completely and some pieces are more atonal than others).
For example, the chromatic scale, diminished scale, etc are all common in atonal music. In fact one method of atonality, serialism, is based purely on the chromatic scale.
A "mode" is a "rotation" of a scale in it's strictest sense. If a scale has no home note then a rotation shouldn't produce much of anything BUT it can! In serialism it is one of the ways of generating new material, In this case a "mode" would shift the notes in time only. In other cases it could simply be used as a device for memorizing things. (Like I used the 3rd mode of the chromatic scale which really just means I started on the 3rd note rather than the "1st")
Atonality is the absence of a key center. Modes are not keys(there is a big difference between C major and C ionian). The problem is that we are so used to keys that we can easily hear them as being part of a key. C Ionian, while different from C Major, has so much overlap that people think they are the same. This does not mean you can't do funky stuff with them by, say, taking a modal progression and using a chromatic pedal tone to ruin the sense of key.
The easiest way to create atonal music is to do the opposite of tonal music. Do not have chords, if you do make sure they are very strange so they do not hint at tonality. Can you have a major chord in an atonal piece? Sure, you can do whatever you want! Some purists may bitch though. Can you make up your own atonal chords? Sure but there are so many more it's better not to think of them as "chords". Could those chords be used in a tonal piece? Sure! The same applies to scales. (the chromatic scale is used in some very tonal pieces)
Remember that tonality is more of a large scale concept. A chord or scale cannot define tonality or atonality. It has to do about setting up the hierarchy of notes. Even atonality cannot avoid this completely and is slightly tonal. Chords and scales are about organizing and nothing more. They are concepts to allow us to reduce the complexity of pitch material. Modes, in their purest form, are simple rotations, again, another organizing tool. Inversions, rotations, Mirrors, etc are all transformation techniques and, at least in some cases, do not imply anything about tonality.
Almost by definition, atonality implies that you aren't following a rigid chord and scale pairing structure. Atonal music doesn't have a key or a central tone. In the context of jazz "atonal" is often used to refer to a song that has no coherent, classic chord structure (i.e. there's no II IV V I type structure in play for the song). The chords follow each other, seemingly at random. The description "atonal" itself gets used in a lot of different situations though. You'll sometimes hear it used to describe music where the melody and chord structure combine to create a generally dissonant sound.
Tough question. I'm really curious to see what others put up for answers. The word "atonal" as a description for music passes beyond fact and musical theory and in to musical philosophy.
According to the Oxford dictionary, the term atonal is applied to music that is not tonal, i.e. not in a key. The term is in some circumstances avoided for music that is serial; and it is sometimes reserved for the post-tonal but pre-serial music of the Second Viennese School (Schoenberg, Berg and Webern). The term ‘pantonal’ is occasionally used in the same sense.
Credits: Oxford dictionary.