# Rock-and-roll Google celebrates analog computing - and Bob Moog

Today's Google Doodle features a simulator for a toy version of the Minimoog synthesiser.

In Google's eclectic fashion, it's meant to celebrate what would have been Bob Moog's 78th birthday.

Moog was a pioneer in electronic music from the 1950s, using the newfangled transistor and analog circuitry to build what were, in short, newfangled analog music computers.

Analog computers differ from modern digital computers inasmuch as they don't bother reducing their inputs and outputs to distinct, quantised, values. Very crudely put, they produce approximate outputs from exact values, instead of producing exact outputs from approximate values.

If you look at the mathematics behind analog computers, for example, you'll probably find integral signs where, in a digital computer, you'd find summations.

You'll find real numbers and continuous functions instead of integers (or fixed-precision floating point representations, which are just integers used in a clever way) and discrete samples.

You might deal with a voltage "somewhere between 0V and 12V", for instance, rather than "a number that has one of the specific values 0,1,2...65535".

Analog computers may be imprecise by modern standards, yet are often capable of performing complex calculations in real-time, even in hostile operating conditions.

For example, consider this problem. As a petrol engine speeds up, the spark plugs need to fire earlier to give the fuel time to burn. This is called ignition advance, and is expressed in degrees of engine rotation. At idle, for example, the advance might be 7°. At 2000rpm, it might be 12°. But above 4500rpm, you might want the advance to be fixed at 20°.

The modern solution is to use a digital mapping - a look-up table telling you what advance to use for which speeds. You end up with an ignition curve which is a series of steps (the rpm range covered by each digitised sample); the size of the steps depends on the quality of the samples and the amount of memory available for the look-up table.

Before digital computers, however, automotive engineers simply hooked up a pair of spring-loaded weights to the distributor shaft.

As engine speed increased, centrifugal effects forced the weights further apart. The weights were linked to a lever which moved - literally advanced! - the ignition trigger switch.

Want to limit the maximum advance? Just add a pin to stop the lever moving past a certain point. Want a slower advance curve? Use stronger springs. Want a funny-shaped advance curve? Drive the lever with a funny-shaped cam.

The input is exact and continuously variable - it's determined by the rotational speed of the distributor shaft. The output is approximate - it will vary with friction, temperature and the age of the moving parts.

On the other hand, the digital map gives an exact answer - the ignition advance is always identical for a specific input. But the input is approximate - it varies only in discrete quanta by time and in magnitude.

So, if you're Googling for something today, have a play on the simulated microminimoog. You can even record and overdub your material on the simulated four-track tape recorder connected to the synthesiser.

Experience some analog computing. Digitally simulated, of course.

(And before you say, "Tape is dead," have a look in the average server room. Sure, it's "digital" tape. But only in name. The underlying principle is the same: record a representative signal as a series of magnetic field alignments in a flexible ferromagnetic layer.)

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### 7 Responses to Rock-and-roll Google celebrates analog computing - and Bob Moog

1. Dan · 563 days ago

The moog doesn't work for me. I click it and all I get is a search for Robert Moog. I'm using Chrome. Of all the browsers it should work in that one, surely?

• Paul Ducklin · 563 days ago

Works for me - I just tried Google Chrome (on OS X) and a prepackaged Chromium Browser (on Lubuntu). Do you have Javascript blocked, or something like that, perchance?

• Dan · 563 days ago

Just flashblock, but I turned it off and it made no difference.

2. Mike Houlden · 563 days ago

Without the Moog,There would not have been Walter/Wendy Carlos' Switched on Bach,KRAFTWERK,DEVO ,etc.the Music industry really boomed with the advent of the MOOG.

3. Howard Freeborn · 562 days ago

doesn't work for me either, Safari...

4. MikeP · 562 days ago

In Electronics we have had a saying for many years comparing analogue and digital systems: Analogue is nearly always right, Digital is nearly always wrong.

An analogue representation has exact values (not approximations) that are constantly varying in step with the original stimulus. A digital representation is a series of 'snapshots' taken at the quantisation intervals and represents the average in that time period and is therefore an approximation that has to be interpolated to return to analogue signals that can drive loudspeakers for example. Digital can have 'clever' error correction whereas analogue doesn't.

In computing, noise can riun an analogue calculation but can be corrected out of a digital process (most of the time). Digital video signals can introduce unpleasant and unwanted visual artefacts in images, just watch a fast moving sport programme (such as F1?). Quantisation errors compounded by low bit rates make some imagery disturbing to watch.

So digital is not always best, is not always the most accurate and not always the most pleasing to the viewer and/or listener.