MIDI out waveforms very different between two devices
RS-232 and MIDI are completely different.
In particular, MIDI uses a current loop; the "space" state (logic 0) is defined as a current of (at least) 5 mA.

Depending on the MIDI output circuit, you cannot simply measure the voltage at a bare pin (or between two bare pins) of the MIDI connector.
Your Korg waveform looks as if you tried to measure a floating voltage, and got noise from something else. (And a sample rate of 80 kHz is much too low to capture the actual MIDI signal.)

You have to measure the current by, e.g., connecting a resistor between pins 4 and 5 and measuring the voltage drop over that.