From Homestar Runner Wiki
Bubs's Keytar was played by Bubs to help supply the music for "The Date of Birth Song" in the email cheatday. He had it handy behind the couch in the basement of the Brothers Strong. It seems that Strong Bad and The Cheat did not appreciate Bubs butting into the song with his keytar. The range is nearly two octaves, from F to E.
The keytar is based on a Yamaha SHS-10 FM digital keyboard. The most common version of the SHS-10 is red and features colored buttons. It was often used as a cheap MIDI controller in the late '80s, as the sounds are nothing special. At around $100, it was almost a toy, but had professional features like MIDI out, pitch-bend, and a two-digit LED display to indicate patch/program changes.
The most obvious differences between Bubs's keytar and a real SHS-10 is that Bubs's only has 24 keys, no visible speaker grill and the neck positioned along the front, whereas a real one has 32 keys, a visible speaker grill and the neck positioned along the back.
In Baddest Of The Bands Bubs called his keytar "Skeezy."