Custom synth by adding notes source and speaker nodes in groups

[nahkd123]

Previously, nodes like "Notes Source" and "Speaker Output" are not usable in groups. You can add them, but they don't have functionality.

This proposal is created to let "Notes Source" and "Speaker Output" be used in groups to turn groups into modular synth thing, which can be used to create a variety of sounds.

• Add support for "Notes Source" + "Speaker Output" nodes in groups
• Add ADSR node
• Add sine wave oscillator
• Add square wave oscillator (with pulse width)
• Add triangle wave oscillator
• Add saw wave oscillator
• Add noise node
• Add Biquad filter (the EQ thing) node
• Add IR reverb node
• Add sampler node (play your sample in loop or one shot)
  • The sampler will be in one shot mode by default. Use synth node if you want to control when the sampler will be played with MIDI input.

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Original issue text:
Stuffs like envelopes simply doesn't work as intended in global nodes network, because they are note-based.

A new "Group Player" node is designed to take an existing nodes group as "synth", then for every note event, it will replicate the group children into a new network, and connect the output signal of that group to output bridge of the player.

The proposed "Group Player" node will have these ports:

• in audioGain: SignalPort: Gain for all notes
• out audioOut: SignalPort: Audio output signal

Notes signals will be emitted from Nodes Source with Default Channel channel and audio signals must be emitted to Speaker Output node.