Drafting to track #16 - some things to fix, but I think this is close. Still need to fix issues with pause behavior and time change clicking, (削除) as well as smoothing filter values (done) (削除ここまで). There also may be some performance improvements to be made, especially with how I am handling interpolating between times.

I modeled this after what I presume is happening with Bitwig's delay effect, which allows for both single echos and feedback delays.

 XFeed In
 ▼
 │
 │ ┌─► XFeed Out
 ┌──────┐ │ ┌─────┐ │
 ┌─►│Filter├────►────┴──►│Delay├───┤
 │ └──────┘ Feedback └─────┘ │
 │ ┌─▼─┐
 In ●くろまる─┴──────────────────────────────►│Mix├───► Out
 └───┘

Issue criteria:

• mix - The wet/dry mix.
• delay - The amount of delay in seconds
• (削除) tap_gain (削除ここまで) - I found this was redundant with the mix and feedback
• tap lowpass - Renamed to feedback_lpf. I think feedback is more generally understood than tap (and should be more accurate in this case as well).
• tap highpass - Renamed to feedback_hpf for above reason
• (削除) enabled (削除ここまで) - Not needed with mix setting
• Additionally, the node will have a custom Stop event to clear the internal buffers.

Additional features

• Feedback - Transforms this node from a single echo into a delay effect with feedback.
• Multi-channel supports crossfeed feedback
• [🚧] Pause/Unpause

Tradeoffs

• The effect uses its own buffers instead of scratch buffers, as channels above a certain amount may result in more scratch buffers being needed than available.
• For mono versions of the node, crossfeed is still an available parameter, although changing its value does nothing.
• From my initial findings, we may be able to simply crossfade between two delay times, and not do anything fancy like stride interpolation. However, I only tested with sine waves.