Hello, new member here. Midi interface problems!

Sorry my first post is to beg for help, and it's not really about MuseScore, but MuseScore supports MIDI input, so I'm hoping someone here has dealt with these problems.

I have an old digital piano, Yamaha Clavinova CLP-123, ca. 1993. It has a limited number of voices. So I figured with MIDI, I could expand a little. I have a laptop with Windows 10, and bought a generic USB to MIDI cable. It has a USB 2.0 plug on one end, a small plastic body with indicator lights at the cord's "fork", and two MIDI DIN connectors on the other end. The body has a stylized, fat treble clef symbol printed on it, and the lights are labeled "IN", "OUT" and "USB". The "IN" light is green and flashes continuously, around 5 times a second. It's annoyingly bright.

I've installed the latest MuseScore and it detects the connection (it sees the generic Microsoft Windows device driver named USB20MIDI), but when I play there's a lag of almost half a second before I hear the notes on the computer. Some notes don't play when I hit them, and some stay sustained on their own. Since I wanted to be sure it wasn't MuseScore, I downloaded another free MIDI workstation program (MidiEditor), and it had the exact same behavior. The notes sometimes play right, sometimes wrong, sometimes not at all, but all the ones that do play have that same delay of about half a second.

Is this a common problem? Is there a solution for it, preferably a cheap one? Am I doing it all wrong, and can I realistically expect to use a PC and software to add new sounds? I was hoping to get Rhodes and Wurlitzer piano sounds to play with. The piano's built-in electric piano sound really stinks.

The instruction manual for the piano is fairly sparse, and the thing was built in 1993, so I won't be too shocked if it won't do what I want, but I'll keep my fingers crossed. Thanks for any replies.