These days signal processing has become one of the strongest facets of audio and music production. The function of a signal processor is to modify an audio signal in some intended fashion, in either the analog or digital realm. While effecting all parts of audio production, processing is most useful in controlling: amplitude level (dynamic range), the spectral content of a waveform (equalization), and effects (such as delay, reverb, recreating room ambience, etc) (Huber, 2001). Keeping these aspects of processing in mind can provide a fresh perspective on some of your favorite songs.
Sherman Keene suggests in his book, Practical Techniques for the Recording Engineer, that there are eight properties of a good mix: 1) Powerful and solid lows.
2) Proper use of the very powerful mid-range areas. 3) Clear and clean highs. 4) Proper but not overburdening effects. 5) Dimension - some sense of depth. 6) Motion - movement of the instruments using pans to heighten the music.
7) At least one true stereo track (e.g., strings, piano, hopefully something used "up front" in the mix).
8) Some acoustic information- not just delays and reverb. This list is rather succinct, but it is finding the most perfect balance of these dynamics that proves to be the art form. Using these guidelines, however, a good mix seems inevitable.
The Roots: "The Next Movement" (Things Fall Apart, 1999)
Here is a great example of a prominent bottom end, which is the hip-hopper's best friend. This mix has got the bass frequencies (60 - 350 Hz) turned up about as far as they will go. The main melody of the song comes from this bass track, which produces a rushing yet grooving feel. The instrumentation of this song consists of: vocals (male lead, fem. bkgd.), electric bass, drums (kick, snare,