Sound design for these models has been undertaken with attention to the relationship between spatial impression and
dynamic range of music, and the physical characteristics of earphones and headphones. 
We have categorized sound creation on music recording onto these two axes: spatial impression and
dynamic range.One way of thinking regards the distance perception. Classical and jazz recordings are thought to be performed with
emphasis on aspects of spaciousness, such as sense of distance, broadness and reverberation. On the other hand, rock,
pops and many of the recent animation soundtrack recordings, spaciousness is not as highly emphasized.
There is thought to be greater emphasis on clarity, which brings the various instruments and vocals to the front.Another approach is dynamic range – in other words, changes in loudness over time. If the dynamic range is wide,
naturally it is possible to use the change in loudness over time to achieve a more dynamic expression of music. But,
there are some types of music for which narrower dynamic range recordings are preferable to allow each of the instruments
and vocals to ordinarily appear before the listener’s eyes.The difference between these two ways of thinking pertains not to which is superior but rather differences in how
music is composed and what is demanded of it. With regard to classical music, and that played by orchestra in particular,
the spatial orientation of instruments is particularly important. Stringed instruments are positioned nearest to the audience with wind
and percussion placed behind them. Should the balance between the spatial orientation and volume of each group of instruments collapse,
the music would disintegrate. For that reason, uniform clarity of sound that allows each instrument to appear before
the eyes of the listener is not demanded of this type of music. Even for classical music, a string quartet, for example,
would have a narrow dynamic range and the clarity of each instrument would be more prominent. For rock and pops on the other hand,
spaciousness is not as necessary as for classical music, and so there is greater emphasis on clarity than spaciousness.
These preconditions are very important, particularly for earphone and headphone listening, and it has become apparent
that the implementation of appropriate target curves and driver design result in deeper enjoyment of music.