Replace the MIDI playback system

[pettter]

The current MIDI playback lags quite a bit even on my fairly beefy laptop. It should not need to do that, I feel, so something is wrong either in the library or in its configuration.

[pettter]

Possibly the problem is more deep-rooted in terms of performance. In particular, loading even a relatively simple example and then just moving the mouse in circles seems to be pretty intense on the CPU for some reason. @meduzen any ideas on what the culprit could be, and what, if anything, would be a good solution?

[yrammos]

@yinanazhou isn’t this nearly fixed now (once #267 has been resolved)?

[yinanazhou]

I will close this issue as soundfont-player is already replaced by smplr in #247.