Circuit Bending

Casio CT-403

The CT-403, or, more accurate, Casiotone 403, was one of the first keyboards with auto accompaniment. The Casiotone 400 series, including the CT-401 (first keyboard with auto accompaniment) and the CT-405 (quasi a MT-68 in wooden casing) can easily be identified by the solid wooden casing, high-quality finish and special design.

The 403 sounds the best in my opinion, so I sold the other "coffins" (the 200 series, as well) and only kept and modified the 403. The tone bank is pretty much the same one the MT-60 has (25 cool sounds!) and the auto accompaniment ranks among the best due to the very phat analog drums and a voluminous bass. The 16 unostentatious beat patterns are accompanied by very minimal chord & bass figures, clearly marking this device as a solo entertainer. After seasonable modifications, however, the character may change rapidly.

The substantial analog technology allows many modifications, but I only built in important basic functions which add zest and overall appeal to its original expression. Changing the latter is a completely different story, but certainly also a very promising one.

• Mute switch for all singular drum sounds
• Decay values of snare and hihat can be altered by switch
• Additional "tempo fine" controller
• Mute switch for bass and chords
• Sustain values of bass and chord sounds can be altered by switch
• Separate volume controls for bass and chord sounds

Sound example