234 | 23 COmPUTER mUSIC
version of the computer, and the basic designs for the new machine were handed over to Ferranti
in July 1949.^6 The very first Ferranti computer was installed in Turing’s Computing Machine
Laboratory in February 1951 (Fig. 23.2), a few weeks before the earliest American-built market-
able computer, the UNIVAC I, became available.^7
Turing referred to the new machine as the ‘Manchester Electronic Computer Mark II’,
while others called it the ‘Ferranti Mark I’; in this chapter we follow Turing’s nomenclature.
His programming manual was written in anticipation of the Mark II’s arrival, and was titled
Programmers’ Handbook for Manchester Electronic Computer Mark II, but it was the outcome
of his programming design work undertaken on the Mark I.^8 Turing’s Programmers’ Handbook
contains what is, so far as is known, the earliest written tutorial on how to program an electronic
computer to play musical notes.
How to program musical notes
The Manchester computer had a loudspeaker—called the ‘hooter’—that served as an alarm to
call the operator when the machine needed attention.^9 With some simple programming, the
loudspeaker could be made to emit musical notes.
The computer’s ‘hoot instruction’ worked like this. There was an electronic clock in the com-
puter synchronizing all the operations. This clock beat steadily, like a silent metronome, at a rate
of thousands of noiseless ticks per second. Executing the hoot instruction once caused a sound
figure 23.1 Baby grows into what Turing called the ‘Mark I’.
Reproduced with permission of the University of Manchester School of Computer Science.