Here’s the quickest way to get started with the Synth:
Add a Modular Synth Component to your actor
Set your Preset–there is a default preset that sounds pretty good, but what I like doing is making a public variable that I can customize with a details panel:

There are a LOT of awesome parameters, as well as a modular patch system at the end:
There are also Blueprint setters for setting individual parameters if you want to do real-time modulation–you can also create Presets within the Modular Synth Preset Bank Asset, which you can break-out as well.
Once you’ve initialized the sound you want, you can activate the sound with the Note On function:
Note value is a MIDI note value (60 is middle C), but it’s float, so you can 'tween if you like.
Velocity is a MIDI value which does volume scale by default–but if you have a non-negative value, it will automatically shut itself off after that many seconds.
Duration is -1.0 by default, if you set it to -1.0 it will sustain until you call Note Off on the SAME note (as it has a polyphonic voice manager).
Here you can see, I’ve a delay to create a similar situation.
The possibilities are limitless when paired with BP logic–we’re looking forward to what all you synth cats come up with!