There are several means by which one can attempt to determine and describe the quality of music with some degree of objectiveness. To begin, some assumptions on which this writeup is based: It is not possible to judge any art in a purely objective manner. All art is not created equal. It is possible to isolate the musical elements of a work from any extra-musical elements, and form a judgement based on these factors. It is possible for the knowledgeable and critically thinking listener to be far more objective and structured in his qualitative judgements about music than the layman. It is reasonable to apply a set of standards to two pieces of art and assert that one is better than the other, as long as one can provide sufficient support for the validity of the comparison and the conclusion.
Note: for the purposes of this node I will alternately address the voice specifically and refer to it under the general heading of "instruments."
1. Quality of technique/performance
This is the easiest category to label as "objective." Instrumental technique is a significant part of musicianship. Obviously a flawless performance is superior to one riddled with mistakes. This mostly applies to live music as few modern commercial artists will leave noticeable instrumental mistakes on their albums.
Music that is more difficult to play demands greater training and dedication on the part of the player. The ability to learn and perform difficult pieces is a large part of what makes us respect someone as a good musician. It shows the degree of control the musician has over his body and his instrument. A good musician plays as though the instrument were an extension of himself and is not limited artistically by a lack of technique. That is, the ideal musician will never find himself unable to execute any given musical idea due to insufficient technical ability. This probably requires the qualification "any given musical idea within reason," however, which again tends toward the subjective, but we must acknowledge that there are infinite ways to compose music that is utterly impossible for a human to perform.
It is important not to assume that the only measure of technique is speed, as some people tend to do. In the first place, speed without accuracy is worthless. Playing with speed and accuracy is difficult and makes up a large part of technique. Other, more subtle elements are important as well, however. Rhythms can often be difficult to execute without being especially fast, particularly in unusual time signatures or with polyrhythms. Many instruments also have their own set of technical qualifications. For example, the use of vibrato on stringed instrument, the ability to hit high notes on a wind instrument, accuracy of pitch on a non-fretted instrument or in the voice, and the ability to sustain a pitch over a length of time, among others, are all measures of technique.
It is also crucial to judge technique separately from composition. One may not enjoy listening to Yngwie Malmsteen, but his technique is still excellent. In terms of affecting the overall quality of music, technique may be considered either in isolation or as a part of the whole. A piece may display virtuosic technique and yet still be of low quality overall, and a piece that does not demand a great amount of discipline from the performer may still succeed.
2. Quality of production
This applies only to music recorded in a studio. One could judge a recording of a live performance based on clarity and instrumental balance, but I will disregard that aspect and focus on record production.
First, a definition. For the purposes of this node I will use production as a blanket term to refer to mixing, mastering, arrangement, and sound quality, though a producer may or may not have a large part in these categories. Sound quality encompasses both the fidelity of the recording (purely objective) and the timbre or tone of the instruments (somewhat subjective).
In modern popular music, bands tend to arrange their own compositions, contrary to the standard practice in the recording industry prior to the 1960's. However, most pop/rock bands don't play horns or strings, for example, so when such instruments are called for (either by the artist or the producer) their parts tend to be arranged and performed by outside musicians. Mastering involves fixing volume levels, adjusting equalization, and numerous other tweaks. It is often handled by a person specifically hired to perform this function.
This category already begins to stray toward the subjective realm, as there are few hard and fast guidelines for what is good production and bad production. It's similar to trying to answer the question "What should music sound like?" The traditional idea of how music should sound on record was based on authentically representing the way the instruments sound to one hearing them in person. With the advance of recording technology, however, this is not always the case.
It seems reasonable to propose that higher sound quality is equivalent to "better" production, and this is often what is meant when one says "good production," but many records succeed despite, and sometimes partly because of, their lo-fi sound. However, in modern music any number of approaches which have been traditionally considered "bad" may be used to achieve a specific effect, not to mention reversals employed to achieve irony (like setting depressing lyrics to a happy tune). These can only be handled subjectively and on a case-by-case basis, and so I will exclude such recordings from consideration here. There are several questions one can ask in order to judge the production quality of a recording:
- Can all of the major instruments be heard clearly and distinctly from one another?
- Does the performance sound natural and not overly doctored or altered? Now that electronic music has become generally accepted, there are times when music can only be said to exist in a completed state after electronic creation or manipulation, but in this case it becomes particularly difficult to isolate production from composition. Disregarding that for the moment, an oft-cited hallmark of a good producer is one who can bring out the authentic sound of a band; that is, what the musicians actually sound like playing their instruments. It does not reflect well on a band if a recording gives the impression that they are relying on studio magic to cover up a lack of talent.
- Do the performances sound convincing? No one wants to hear a band phone in their performance on record. A good producer should elicit, identify, and use the best possible performance a band has to offer.
- Is a variety of instruments utilized in a given song, or over the course of a given album? Does the choice of instruments and the timbre of those instruments effectively communicate the ethos of the music? Do they sound as delicate, powerful, mellow, urgent, angry, close, distant, flowing, stumbling, joyful, or sorrowful as they should in order to best evoke the character of the music? Does the choice of which instruments are used and which instruments sound most prominent feel appropriate? This can also include the quality of the vocal delivery, which falls under performance/technique as well as production.
- Does the record have varying dynamics? Dynamics are a common element in good composition, but some albums are produced in such a way that any semblance of dynamic variation is destroyed. The loud sections of music are meant to be loud, and the quiet parts are meant to be quiet. Most listeners don't want to have to constantly adjust the volume when listening to a record, but when dynamic variation is written into a piece and then squashed during production, the result sounds weak and uninteresting.
There are many other aspects of production and arrangement which cannot be judged objectively, but which may be valid reasons to like or dislike an album.
3. Quality of Composition
This is perhaps the most difficult category to judge, but it is also the one in which many listeners are most lacking in knowledge. Discounting lyrics, which I consider to be outside the scope of this node, there are two main areas in which composition can be evaluted:
Melody. This is the first thing most people notice in any musical composition. There are many things that can make a melody effective. Is it interesting or unpredictable, rhythmically and/or intervallically? Going straight up or down a scale is not much of a melody; a repetitive sequence is only slightly better. Good melodies tend to use more than a couple of notes and will often blend multiple scales and employ chord tones as well as non-chord tones.
There are many types of melodies; theorists describe a melody using stepwise motion as conjunct, while a melody with large leaps is called disjunct. Good melodies often make use of both types of motion. While a good melody may be unpredictable, it should have a sense of logic or syntax. Call and response melodies consist of phrases that complement one another, creating a sense of logical progression.
Is it catchy? Melodies can be catchy without being very good (like lots of music on the radio) but if it gets stuck in your head then it's doing something right. Good melodies are often described as lyrical or hummable, be they vocal or instrumental.
What separates the men from the boys in terms of melody-writing, however, is development. This is what is missing from many pop songs which are catchy but ultimately vacuous. Writing a good hook is a start, not an end. Classical forms emphasize exposition and development, but modern songwriters are often content with presenting one idea and repeating it ad nauseum. A good melody will grow and vary in the course of a piece. If you've heard all that there is to hear within the first minute of a song, there's no reason to keep listening. There are several methods of variation besides melodic variation, but it is nonetheless important.
Harmony. Harmony refers to the effects created by multiple notes sounding simultaneously. Harmony can refer to chord progressions or complementary parts performed together. A common technique is to introduce a simple melody in the beginning of a piece and vary it throughout by adding more complex harmonies. Pachelbel's Canon uses such a technique. Many will say that complexity doesn't equate to quality, and this may be true, but it is not always the case. Anyone can come up with a melody, but it is the setting and treatment of that melody which requires skill. Simplicity is often beautiful, but simplicity can be found within complexity. The Ode to Joy theme from Beethoven's 9th symphony is extremely simple on its own, and yet it lies at the center of a complex masterpiece. The idea of avenging one's father is a simple concept, and yet Hamlet is a very elaborate work with myriad possible interpretations. Complexity for complexity's sake is meaningless, but elegant, structured complexity is the work of a great mind.
Repeating the same melody over changing chords is another method of variation. The chords played beneath a melody can totally alter its character. Interesting chord progressions are also part of good composition. Pop songs aren't known for chordal complexity, but a little mode mixture or some extended chords can go a long way (SEE: The Beatles and The Beach Boys).
It will never be possible to evaluate a piece of music with complete objectivity, but educated arguments can be made as to the relative merits of a work. The most important thing is to listen intently and with a critical ear. If you find music enjoyable or if you hate it, ask yourself what it is exactly that makes you feel that way. Then try to separate the aspects which involve your personal background/taste (I don't like the sound of his voice) from the aspects which involve musical quality (He's a bad singer: he's out of tune, his range is limited, etc.). Investigate as much music as possible in a variety of genres. Listen to music that critics hold to be classic, but don't take their word for it. Remember that music can be entertainment, art, or both. Always keep your mind and your ears open, and keep enjoying music.