I'm not sure where this topic is going after reading through this thread, but I thought I would try to tackle the original questions myself. These are my opinions; I assume nothing that I have written to be incontrovertible.
What is the limit of music? Does it need to make a sound? If you assume rhythm is music (as most do) then how could soundless pressure (say on ones arm) in a rhythmical pattern not be music? Yet it makes no [audible] sound. Also, if you are stimulated to imagine a sound, while now sound being present is that music? (Yagan Kiely, 2007)
As far as limitations in music go, from the perspective of a composer, I would believe that its limitations can be stretched depending on how much sound any composer can hear in his head at any given point in time. In terms of its substance, I would also think that an important limitation in music involves the question of what constitutes order or structure, which could be established in an improvisatory manner, a highly established system of mechanical processes as well as compositional approaches, by a random and indeterminate pattern in the case of John Cage, or even by taking random sounds and reordering them to one's interest (musique concrete). All of these depictions of musical order are different from each other, and in my opinion, they form a hierarchy of musical order.
As far as whether or not music needs to make a sound, I both agree and disagree, depending on how far I would take the subject. If I were in a vacuum, it would be impossible for me to create an audible sound because the characteristics of a vacuum prevent sound from traveling through it, yet even soundless pressure expressed in a rhythmic pattern could be music as it doesn't involve just hearing it but feeling its touch as well. If one were stimulated to imagine a sound, that can be music. Jazz solos involve imagining sounds that would fit under chord changes in a 32-bar AABA song form, 12-bar blues, or even a 24-bar AAA' song form, and this goes on while hearing the chord changes in the guitar, bass, and keyboard. Perhaps the true implication of the question involves the independence of the sounds imagined in his head relative to the sounds present around him. If that is the case, it depends on the function of the sounds imagined in one's mind in relation to the sounds around him. That matter in itself is subjective, depending on what anyone may imagine to be practical vs impractical.
Why does music have to be melodic? Obviously it will make it more pleasant to the ear but that doesn't inherently stop unmelodious or noisy sounds from from being music. Theoretically and sound can be musical, white noise can be seen as a extremely complex music. (Yagan Kiely, 2007)
It is not absolutely and indisputably necessary to have melody in music as it is an element of what can be applied to music. Just playing a series of chords on a piano using functional tonality would certainly fit the idea of music since the harmonic progression played on the piano creates a sense of order. In certain areas of music, however, melody is essential to the framework or structure. In jazz, for example, where solos require a melody and chord changes to solo over, it would be essential to have melody. Otherwise, it would be very difficult to find a jazz chart memorable, like "Autumn Leaves," "So What," or "West End Blues." Melody would also be essential in any music composed in the style of theme and variations. Otherwise, if a composer didn't have a theme to write variations for, what would the point be of writing variations without a theme? Sure, we could argue that it may be possible to write variations on John Cage's
4'33", if we could consider that our experiences during those four minutes and thirty-three seconds can have variations, depending on our state of mind wandering from one variation to another, but that does not fit the historical definition of a theme and variations in terms of its context. For that reason, doing a variation on something like this would be impractical and maybe counterproductive to one's intentions. (I liked the reference to white noise here, where I would also say that pink noise can also be seen as extremely complex music.)
Take the tree, it is natural, it is peaceful. Mahler and several other composers (especially of the Naturalist [romantic] era) imitate the sounds of nature, take Mahler's 1st 2nd and 6th symphonies, or Messiaen's Catalogue D'oiseaux (Hie piano music that imitates various bird calls). If search to imitate it withing music, why cannot be the source also music?(Yagan Kiely, 2007)
I would agree here too. Nature has its own array of sounds that make it musical. Especially with the rapid advances of electronic music, sounds found in nature can be recorded and rearranged into music. The sounds of the leaves on the tree blown by the wind can certainly be seen as something musical.
For the purpose of this I am assuming that a tree can be music. Who is the composer? I am limiting this discussion to a primarily Atheist view so I am not taking into account the option of a supreme being as the composer. Is nobody the composer? The wind the composer? The tree? Of the listener? It is my opinion that indeed the listener is the composer, for he or she may listen and disagree or agree with the composition in different ways. appreciating, construing and organising the given information of sound in their mind. They are I believe the composer because of this process. But here I come to a predicament, a paradox if you will. Is that process a version of orchestration, or composition? (Yagan Kiely, 2007)
Anyone who creates order is a composer of some kind. Anyone who creates disorder in an orderly fashion can also be considered a composer. Both of these ideas involve some form of decision-making and sound rather contradictory, but perhaps I could explain the latter idea like this. I think of disorder created in an orderly fashion as a process of having fixed ideas within a piece of music that has no fixed outcome. Morton Feldman's
Durations from the early 1960s is a great example alluding to what I'm implying. The pitches assigned to the instruments in the piece themselves along with the choice of instrumentation given to each of the piece's movements demonstrate some predetermined quality, whereas the length of time for the instruments to move from one pitch and the question of which voice will move next are indeterminate themselves. Here, disorder is found in indeterminacy, and order found in what is predetermined.
As to the last question, composition and orchestration are not exactly the same. Semantically, orchestration is more specific than composition, as orchestration involves the layering of various instrumental parts to harmonize and strengthen melodic and harmonic materials, a term that I would consider to be more of a derivative of composition. Composition is in my opinion broader in context, which would imply the creation of an idea, the management of how the idea will be structured, and the determination of how that idea can be most effectively expressed to the listener (or reader for anyone who writes). In terms of the way a person listens to something and interprets the information, the idea fits more closely a version of composition since the application of aural skills needed to accumulate information from the music being played in terms of its structure, pitch/melodic content, and harmonic analysis follows more closely a compositional device, not an orchestral device. I would only consider one's construing of the information to be a process of orchestration in two different ways: if the listener was processing specifically the blending of the instruments themselves or if the listener was watching a ballet, opera, or film and determining the compatibility of the instrumentation to the scenes or theatrics found within them.