Music Arrangement and Methods of Multiple Access for Shared Medium Networks.
August 19, 2005, 12:59 pmI'm sure this is not an original thought, but I feel like writing about this.
The past year and a half, I've becoming increasingly interested in arrangement of music. I think an interesting arrangement can make a song that's just okay really great. And since I've been thinking about arrangement, I noticed relationships with other something I had to study in school: multiple access for shared medium networks, like cell phones and radio.
And really, the audio spectrum is a shared medium network and it has a limited amount of bandwidth to send messages (or music), and there are several ways of transmitting multiple, unique messages (or instruments).
One method is simply to arrange the music so that different instruments play at different times. For example, bass guitar playing notes on 1 and 3, while the rhythm guitar answers on 2 and 4. It's easy to differentiate between the bass and rhythm guitar because they're not overlapping and each has it's own space in the medium.
This is a perfect implementation of Time Division Multiple Access (TDMA), one of the techniques used in cell phones. From wikipedia:
It allows several users to share the same frequency by dividing it into different time slots. The users transmit in rapid succession, one after the other, each using their own timeslot. This allows multiple users to share the same transmission medium (e.g. radio frequency) whilst using only the part of its bandwidth they require.
Another arrangement technique is to write parts for instruments whose frequencies are separate. For example, if the vocal part is primarily around 440 Hz, maybe the lead guitar part should be around 1600 Hz.
This is analogous to the oldest method of multiple access, Frequency Division Multiple Access (FDMA). Again, let us turn to the glorious wikipedia:
In FDMA, each transmitter is assigned a distinct frequency channel so that receivers can discriminate among them by tuning to the desired channel.
Sound familiar? If you've ever used AM/FM radio, you know what I'm talking about. Hrm... too bad I can't think of any relationships between music arrangement and amplitude modulation vs. frequency modulation. I guess I could mention that vibrato/tremolo and amplitude/frequency are synonyms.
While the goals of multiple access for shared medium networks are quite similar to problems involved with arrangement, they are not the same. It is of the utmost importance that multiple access for shared medium networks keep the signals separate (it would be annoying to hear crosstalk on your cell phone from another conversation (which I hear used to be a genuine problem)). But the signals of musical instruments were meant to be blended. The way string instruments can blend with organ and background vocals making it impossible to differentiate the sounds is a great thing! Listen to Pet Sounds (in mono) and just try to differentiate guitar from piano from electric piano!
Yes, this is what I think about. I'm sure I've said somethings incorrectly, so don't hold me to it.