synth 3

Figure 8 summary

• scale to 0 - 1
• invert amplitude range
• use note as decay time
• attack and decay
• filtered noise
• amplitude envelope

Filtered noise drums

Our third synth creates splashes of noise in different frequency bands so it can be used for snare or hihat like effects. We filter some white noise using a bandbass filter, [bp~ 100 0.5] which has its center frequency controlled by the MIDI note frequency.

Inverting and scaling a control

You can see how we adapt the MIDI note number so that we get a quieter and shorter sound when the frequency is higher. Dividing the full note range 0 to 127 with [/127] gives us a normalised value from zero to one. The combination of [swap 1] and [-] is an idiom that inverts a normalised signal, so that it ranges from one down to zero as the input increases. A [swap] object exchanges its inputs, so when used with [-] we get 1 minus x for an input x.

Substitution in lists

For an envelope we have used an ordinary [line~], activated by a message producing a variable decay envelope. The decay range is substituted in $1, a value ranging between zero and 400 milliseconds. Notice the second part of a message to [line~] can be omitted when it's a zero in the first position. Where we use $1, $2 etc9 in a message box, each is replaced by the value of any corresponding list element that appears at the message box inlet. In this case a float in the range 0 to 400 will replace $1 in the list so it becomes something like [1, 0 390(, the MIDI note now controls the decay time.

Output EQ

Finally we sculpt the frequency range of the filtered noise with a little EQ in the form of a [lop~] final stage, and then boost it back to reasonable level. [lop~] is a simple low pass element with one parameter for its cutoff frequency.

Notes

Do not use $0 in message box lists as this has a special meaning.

Figure 8: synth3

F-synth3.pd