A piece of music can be described according to many parameters. Please note that overusing the terms described below can easily lead to pigeonholing an artist or a genre and tying them to specific arbitrary traits. My deliberations are thus not meant to categorise all music because the categories we choose are mostly vibe based. I am also in no way assigning any value to any parameter. My goal is to explore the limits and edges of spectrums, to find new, possibly uncharted forms of music. I will be relying heavily on an analogy to the political spectrum, specifically the concept of the overton window. In this context it will refer to the section of a spectrum that contains most contemporary music. When setting out the spectra I did my best to make sure that each spectrum is independent of the others, meaning it's possible to create music that differs in only one spectrum. Though it's not fully possible, I tried to make defining the parameters not culturally dependent. My ideas for non-conventional music certainly don't exhaust all possibilities. I encourage You to explore them further and contact me if You find something interesting.
Possibly the easiest parameter to measure. The slowest pieces within the overton window are about 50BPM, the center is about 100-130BPM, and the fastest conventional pieces reach up to 200BPM. It’s quite easy to imagine creating music on both extremes of this window. Music slower than around 50 beats per minute becomes so slow, that humans stop being able to feel the relationship between pulses as a steady rhythm. Meanwhile pulses faster than around 200 beats per minute are so fast, that individual hits stop being discernable. There is music in both of these extremes. Adam Neely made great videos on them: [1] [2]. Furthermore there already exists music outside of this binary spectrum - a good example is ambient, which doesn't have tempo. Arythmic and instant music can also be understood to exist outside of the spectrum (see: rhythmic complexity).
This one is more subjective and cultural - some rhythms are very common in one tradition and alien in others. Despite this it may be possible to objectively determine the complexity of a song's rhythm. This is not my intention here however. In general we can say that one edge of the overton window is simple rhythms in common time signatures, emphasising the main pulse while the other uses polyrhythms, complex time, syncopation and other techniques. I’m more interested in the limits of this spectrum. The simplest possible rhythms are monotonous pulses in the vein of minimal techno. The other extreme is the absurd rhythmic complexity commonly explored in genres like breakcore or fusion. The aforementioned ambient is outside of the spectrum (no rhythm). We can also imagine other “arythmic” music, with pulses that are not organised in any manner, for instance utilising computer generated randomness. I coined the term “instant music” to describe songs made up of a single event. Because rhythm is defined as a temporal relationship between events such music has neither rhythm nor tempo (examples in [3]). Instant music is a fascinating vehicle for experimentation despite its apparent simplicity. Bill Wurtz is the master of instant music.
In my opinion this can be unequivocally determined for any song. Structure is the way different motifs and ideas are arranged within a composition. On one end there are simple verse-chorus structures (ABAB…), while on the other - a progressive song structure common in prog-rock and its derivatives, without one repeating chorus. The conventional centre in contemporary music is the classic ABABCBB structure. Extremely simple music has only one repeating section (AAA…) while extremely progressive songs don't repeat any idea. To get outside of this spectrum we have to think a little abstractly. Instant music which I described earlier fits the definition of extreme simplicity (only one idea) and technically also extreme progressiveness (nothing repeats). Other ideas for “post-structural” music include endless music (for instance utilising random generation) and the hypothetical startless music, I think this is a very exciting area for research.
Here authenticity refers to whether a piece of music utilises natural, acoustic sounds or sounds that require synthesis, sound processing and so on. One end of the spectrum includes acoustic, live music while the other is electronic music for instance. The idea of a centre here is heavily culturally influenced and in the west has moved significantly to the electronic music side in recent decades. Today it encompasses “normalised artificial” sounds, like distorted electric guitars, synths and autotune. Extremely natural music utilises human speech and nature sounds while extremely artificial music is mostly artificial noises and sounds that don't try to emulate any conventional instrument. Outside of the spectrum we can imagine for instance sounds of nature from other planets.
Possibly the least objective parameter. On one side there is a soft voice and clean tones while on the other - heavy distortion, aggressive vocal techniques and noise. In the west the centre includes overdriven guitars and rock singing. Extremely soft music doesn't have any clear attacks, like in ambient whilst extremely intense music is stuff like harsh noise. Outside of the spectrum we can conceive various ways of synthesising these extremes, for example playing sounds associated with softness extremely loudly in unexpected moments