BTW, even if you don't have a keytar, any of us can try this as an exercise.

Set up a guitar patch (acoustic, electric, no difference) to whole keyboard mode, piano mode on, pick a style, glue that LH to the wheel or lever, and have fun!

Want to take it further..? OK. Now forget about the wheel, and do it with your LH. Play a melody, be careful about sticking to two notes or less to not retrigger the chord until you WANT to. Master this, and you can now chord the arranger and play counter-melodies in your LH while you solo or play the main melody in the RH!

Another really cool use for this is, set up your LH side to be a slap and pop bass patch, but set the velocity up so it doesn't sound until you hit it REALLY hard. Now, you can chord without anything sounding, but every now and again, you can pop a bass note out when you feel like it. This is something bass players do a lot in funk, soul, pop musics... finger style mostly, pop bass to help the turnarounds or rhythm every now and again.