# Core

The *Core* plugin is actually not a plugin at all.
It's built in to the Rack application itself, but you can add Core modules to your rack just like normal modules.

### Audio
![Core Audio](images/Core/Audio.m.png)

The *Audio* module merges the virtual Rack world with the physical hardware world.
The **INPUT** section sends up to 8 Rack signals to a hardware audio device for playback, and the **OUTPUT** section sends up to 8 hardware signals into Rack.

*Audio* currently supports the following **drivers**.
- Core Audio on Mac
- WASAPI and ASIO on Windows
- ALSA on Linux
- VCV Bridge (described in a below section) on all OS's, although there are no Bridge plugins for Linux at this time

After a driver is selected, a particular **device** can be chosen for the driver.
If the device has more than 8 inputs or outputs, you can select the desired range of outputs, offset by a factor of 8.

The **sample rate** is the number of audio samples per second for the audio device to process.
Note that this rate is different than Rack's internal sample rate set from the toolbar at the top of the screen, which determines the number of samples per second for virtual Rack modules to process.
If set to different rates, sample rate conversion will occur, resulting in slightly higher CPU usage, slightly less audio fidelity, and slightly more latency.

The **block size** sets the number of samples to store in the audio buffer before releasing to the audio device.
A higher size results in more latency (`blockSize / sampleRate` seconds), but a lower size requires your operating system to communicate with the audio device more frequently, resulting in potentially less audio stability.
A good balance can be found by increasing the block size until no audio "glitches" are heard.

Note: Using multiple Audio modules is experimental and may crash Rack or render unstable audio.
Most DAWs avoid this feature entirely by restricting audio to a single input and a single output device for stability reasons, but if using multiple audio devices in Rack works with your configuration, more power to you!

### MIDI-1
![Core MIDI-1](images/Core/MIDI-1.m.png)

*Coming soon*

### MIDI-4
![Core MIDI-4](images/Core/MIDI-4.m.png)

*Coming soon*

### MIDI-CC
![Core MIDI-CC](images/Core/MIDI-CC.m.png)

*Coming soon*

### MIDI-Trig
![Core MIDI-Trig](images/Core/MIDI-Trig.m.png)

*Coming soon*

### Blank
![Core Blank](images/Core/Blank.m.png)

Useful for adding space between modules in your rack.
You can resize the panel by dragging the edges horizontally, with a minimum size of 2HP.

### Notes
![Core Notes](images/Core/Notes.m.png)

Useful for adding patch notes, section titles for organization, instructions, and author information to your patches.
You can copy and paste text with Ctrl+C and Ctrl+V.

### VCV Bridge

Rack is a standalone DAW-like application and not a VST/AU plugin because of the major limitations of these formats.
It is common to think of physical modular synthesizers as entire self-contained DAWs, and many people use Rack as a complete DAW to compose music and build patches without other software.

However, *VCV Bridge* allows audio and MIDI to be transferred between Rack and your DAW through the included VST/AU Bridge plugin.
Currently VCV Bridge is only a VST/AU effect plugin (Mac and 32/64-bit Windows) for using Rack as a send/return on a DAW track.
VSTi/AU instrument plugins, MIDI, and DAW clock transport are coming soon in a later Rack 0.6.* update.

Setting up Bridge in Rack and your DAW is easy, and setup order between the two applications does not matter.

#### Setting up Bridge in your DAW

- Make sure the VST or AU Bridge plugin is installed, and launch your DAW.
- Add the "VCV Bridge" effect plugin to an audio track.
- Open the plugin parameters (e.g. by clicking the plugin's triangle arrow in Ableton Live) to reveal the Bridge port setting and 16 automation parameters.

#### Setting up Bridge in Rack

- Add an Audio or MIDI module to Rack (from the Core plugin), and select "Bridge" from the driver dropdown list.
- Open the device menu to select the Bridge port.

Up to 8 channels of audio entering the Bridge effect plugin are routed to the INPUT section of the Audio module in Rack and then back to the effect plugin.

The 16 automation parameters in the VST/AU Bridge plugin simply generate MIDI-CC messages 0-15, so you can use a Core MIDI-CC interface to convert them to 0-10 V signals in Rack.