Better SoundFont Synthesizer

[spessasus]

Is your feature request related to a problem? Please describe.
The current synthesizer doesn't support soundfonts particularly well and has issues, such as the 0-tick long drums. It doesn't seem to support the modulation envelope or the soundfont modulators, nor any system exclusives or the SF3 format.

Describe the solution you'd like
I propose integrating my SpessaSynth synthesizer as it resolved all those issues. It has full SF2 support and even DLS support and is written in JavaScript. SF3 support would also mean that a better soundfont could be used as the default with compression. I'm thinking of GeneralUserGS, but that's up to you.

Describe alternatives you've considered
Another option is js-synthesizer by jet2jet which uses a Webasssebly port of fluidsynth as the backend, though that solution does not support DLS correctly.

[Pizzabox96]

yeah add dls support

[ryohey]

@spessasus I just checked out the spessasynth and it is really great! awesome work! I'll see if we can integrate it into signal.

[liangliangmusic]

To support sf3 will be really nice. We are looking for the function for a long time.