In the late 1960's, while a graduate student at Indiana University
(Bloomington), I ran across a music school student named Donald Byrd
(now better known for a music notation program of considerable capa-
bility) who at the time worked at the campus's Research Computer Center
(the name Wrubel (sp?) was attached later).  He taught me the theory of
generating tones via a chain line printer.

As mentioned a day or so ago, these printers had a character set
mounted on a chain which rotated across the page at high speed;
a solenoid fired (yes, there was a solenoid for each print column)
whenever the desired letter on the chain passed over the appropriate
column.

The way he would generate his highest pitch was to print the same
letter in every column across the page; the chain was moving fast
enough that this print procedure produced a kind of midrange tone
as successive solenoids fired.  The next lower available tone was
generated by printing a given character in _every other_ column across
the page; half as many impacts in the same amount of time, so it was
an octave lower.  The next tone was a letter every third column, so the
pitch was what you would expect--an octave and a fifth down.  Every
fourth column produced a tone two octaves down from the top, and so
forth.

This readership will, of course, be familiar with the harmonic series
of partials, sometimes called an "overtone" series.  Well, this set of
pitches was similar except successive pitches were lower rather than
higher -- if you will, and "undertone" series.  Some of us who studied
the history of music theory laughed at this description, because some
theorists had looked for an occurrence of an undertone series in nature
to act as a natural phenomenon justifying the minor mode, in the way
that the overtone series seems to justify the existence of major.  But
the theorists never found one.  At least, not until Don Byrd and his
chain-printing undertone series.  A minor musical miracle.

Michael J. Babcock