Treebeard's Homepage : Stumpers

Treebeard's Stumper
8 November 2002

Sound Tracks

During our afternoon classes at Dunn Middle School, we can't help overhearing Donna's brass band kids practice. At first I thought about barnyards, but now there is some harmony! Here are two stumpers with a curious connection. How can the same note (like middle C) sound so different on a flute, trombone, and sax? And how can any band be recorded on the single sound track of a tape or CD? If a cat and dog walk in line, we can easily tell who made each footprint. But a microphone can only record a single track of sound with everything at once. How can we still pick out each instrument in the recording?

Our beloved Dunn School band teacher Rose Knowles calls the lovely sound of beginning band students the Calling of the Geese. But after just a few weeks our DMS students are producing sweet harmony. This is a two-pronged stumper. All those band instruments sound different even when they are playing the same note. And all those sounds can be recorded in a single (maybe stereo or surround) sound track that looks something like this:

This is really a sample of Bix Beiderbecke's classic Royal Garden Blues, with brass, woodwinds, piano, bass, and drums all at once. The bumps along the groove of a mono 78 or LP record would look something like this up close, as would the magnetic flux variations of a cassette tape or the digital signals of a CD or MP3. How can all that great jazz fit on just one wiggly track on any recording? Which instrument made each bump?

The real question is what's the connection between these two stumpers about playing and recording music?

Answer


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Copyright © 2002 by Marc Kummel / mkummel@rain.org