Because it is harder to evaluate and is more subtly presented than visuals, audio is an aspect many reviewers forget to mention. Even though you do not have to write paragraphs on the matter, the fact that it is present in the form of music, sound effects and voice acting makes it such an important facet of the anime experience that it should definitely not be overlooked. Like everything else, your opinion on the matter should gradually form as you watch the anime and not at specific parts. For example, it is easy to rate and dismiss anime music after watching the opening animation, but that is just scratching the surface of a huge portion of anime making. Completing the entire anime, and not just an episode, before making up your mind is the only way to efficiently rate audio in anime.
1) Music. Music is normally used to accentuate the mood and emotions in particular scenes, so before asking yourself if you enjoy the music in an anime, first ask yourself if it succeeds in making the drama more intense, the comedy funnier, so on and so forth. This can be the case even when music is so lightly used you have to concentrate to hear it, or when there is no music at all; in key moments, silence is sometimes the best music to emphasize the mood, yet it can often flirt with awkwardness.
Then again, it is important not to pretend to like the music because you think it fits the anime well. As long as you keep an open mind, your taste in music is a valuable part of your opinion. Also, do not forget to check the soundtrack for repetitiveness. Overused melodies are never appreciated whether in either short movies or long series.
2) Seiyuu. I cannot stress enough the importance of good voice acting. Just as acting is primordial in live-action movies, seiyuu work often makes or breaks anime, especially the ones with dramatic situations. One could easily go crazy trying to separately evaluate every character’s seiyuu based on every line they say. But rest assured the good ones will stand out, as do the bad ones. There are key scenes where acting is especially important; these should give you a good idea of the voice actor’s worth, which, even if it is not always the case, is usually relatively constant throughout an entire feature.
As for what qualifies good or bad voice acting, the best way is to compare the character (age, sex, background) and personality to the voice he or she is given, then evaluate the effect of his or her lines and overall performance on you in all of the key moments. Did the character itself make you laugh, cry or throw things at the screen? Do not hesitate to mention if you found seiyuu‘s voice to be excessively annoying. Even if it may not be the voice actor’s fault, it still deters your experience as a viewer.
3) Sound effects. You have to remember that every sound you hear in an anime was added afterwards. The birds chirping, the footsteps… the attention to detail in ambient sounds is significant when it comes to things we usually take for granted in live-action movies. Animation studios do not necessarily create real explosions and gunshots for sound sampling; many sound effects are synthesized, and their faithfulness is completely debatable. Chances are, though, if you do not really notice the sound effects, they are well-timed and well-chosen.
Location-specific sounds contribute greatly to a given ambiance. When there are few background noises in public places, or if most sounds seem to have been created by a keyboard, the readers must be informed. On the other hand, if an anime manages to stand out by its sound effects, it is unquestionably worthy of a mention.
This all seems a lot to remember, but the trick is to just sit back and enjoy the anime without thinking too much about music, voice acting or sound effects, then look back at the whole, just like your readers probably will. After watching a lot of anime, you will be able to pinpoint what you like and dislike. Everything should come naturally.