synth 4

Figure 11 summary

• poly voice
• 3 note poly chord
• separate trigger from list
• sustained envelope
• unpack the notes from list
• send to 3 voices
• mix and scale

Poly synth

To make chords we need more than one note. Although we could treat each synth as a monophonic instrument and build up harmonies by careful sequencing, sometimes we like to be able to specify block chords that will be played in a polyphonic way. To do this we first design a single voice of the instrument. This synth is a variation on our first sinewave instrument. It has a vibrato and MIDI note input. Control of the final signal amplitude is just one multiply, so the instrument is not capable of playing separate notes as such, only chords that start and end together.

3 voice synth

You can see three of the voices arranged with the frequency of each controlled by the corresponding outlet of the [unpack] unit. [unpack] splits up the list of notes sent as a chord by the sequencer. We separated the envelope trigger from the note list using [t l b] and use the bang to activate the envelope message box.

ASR envelope

Notice also that the message to [vline~] has a softer attack and a significant delay before the decay stage, which causes the chord to rise in 35ms and hold for a further 165ms, the remainder of the delay time, then fall to zero in 100ms each time it plays. Because 3 voices will be playing at normalised level we need to divide the output signal by 3 to get it back into a normalised range.

Figure 11: synth4

H-synth4.pd