##### Scope~, Number~, Spectroscope~

In this lesson (in class) you have seen the object *number~* several times.

This object has turned out very useful because it allows us to see what happens in numbers inside a signal. If scope~ and spectroscope~ give us a visual representation respectively of the time domain and frequency domain of a signal, with number~ we literally can see the variation in pressure as amplitude oscillating from -1 to 1.

Number~ is useful to show the various modifications a signal can take if multiplied, subtracted v.ia the mathematical signal operators. A signal oscillating from -1 to 1, if multiplied by 100, it will then oscillate between -100 and 100 (e.g. it is used in FM synthesis, for the modulator); a signal that needs to be reduced in amplitude as it is too loud, if multiplied by 0.5, will tunr out to osicllate between -0.5 and 0.5.

##### Mathematical operators

Mathematical operators are objects that perform math in Max. They can be data math operators or signal math operators. The right-to-left Max rule is on with data math operators: a number into the right cold inlet cannot produce any output unless some other data has passed through the left hot inlet:

With audio signal math operators instead, although there is always a right-to-left computational order, the output is always present and updating, as the right-to-left computations complete very quickly.

##### Different uses of multiplier object *~

In this Lesson 2 we have seen multiplier used in three different ways. It can be used for:

- amplitude control (identical as using a gain~ fader to control volume)
- modulation
- mixing signals

Modulation is a form of amplitude control, in continuous change as it is done by an oscillator.