of Microprocessors

140 MUSICAL ApPLICATIONS OF MICROPROCESSORS
Macintosh computer was just recently expanded to 512K of memory because
its original 128K was deemed inadequate for the needs of its extremely
complex software. Since the cost of memory is so low and continues to
decline, there is less interest now in space-efficient programming techniques
and more in time-efficient ones, both for the programmers and for the
machines.
The amount of memory actually needed is largely determined by the
application. In later discussion, three broad classes of microprocessor
applications in music will be explored. These are logic replacement in actual
synthesis and control circuitry, general-purpose computers that control external
synthesis circuitry, and very powerful general- and special-purpose computers
that perform direct computer synthesis. Accordingly, the logic replacement
application requires the least amount of memory, often only a few thousand
bytes, while additional memory can always be put to effective use in a direct
computer synthesis system.
Mass Storage
Next to main memory, external mass storage is the most reliable indicator
of overall system capability. Further, the type of external storage used
has a great influence on typical system operating procedures. A system with
no external storage at all is extremely limited in general-purpose applications.
The earliest microcomputers, if they had any mass storage at all, often
used punched paper tape. This was the natural result of using a teletype
machine for text input and output, but it was very slow (l0-50 bytes/sec),
noisy, and the tape was nonreusable. Another often-used early storage
peripheral peculiar to microcomputers was an audio tape recorder. It turned
out to be fairly easy to program a microcomputer to generate audio signals
dependent on the data to be saved and then recognize them on playback to
recover the data. Generally, the encoding/decoding circuitry was simple, and
cheap portable cassette recorders were adequate, which meant that audio
cassette storage could be implemented for less than $50. While faster,
quieter, and cheaper to run than paper tape storage, the recorder still had to
be manually operated and the stored data could not be edited in a
straightforward manner. In the late 1970s, some experimental products using
program-controlled cassette decks were introduced in an attempt to overcome
the manual operation and editing problems, but none was successful. Even
now, one occasionally hears of a new low-priced microcomputer that uses
some kind of tape cartridge for low-cost storage, but then invariably the
manufacturer offers or completely switches to disk storage instead.
Floppy Disk
The flexible or "floppy" disk is a relatively new mass-storage device that
seems custom made for microcomputer systems. Introduced by IBM in 1970