Casio CTK-691

CTK-691 is a 61-key portable Casio keyboard which has a ZPI sound source, DSP effects and a drawbar organ function. Its Internet Data Expansion System allows users to download resources from the internet, such as waveform data. The model has 566 preset tones (300 Advanced tones, 50 drawbar organ tones, 128 GM tones, 72 various tones, 16 drum sets), 156 rhythms, 232 digital effects (16 reverbs, 16 choruses, 100 Preset DSP, 100 User DSP), 32-note polyphony, a layer/split function, 3 levels of touch-sensitivity (can be switched off), a 16 channel mixer function and a digital equalizer.

The Casio CTK-691 has a synthesizer that can edit and create new tones. Using the synthesizer while the drawbar organ function is on lets the user control the drawbars manually. Because this model is compatible with General MIDI, it includes an SMF player which lets store MIDI files that have been uploaded from a PC. A song memory function with a maximum of 6 tracks lets record pieces using either real-time recording or step recording. A Piano Setting button is also included which, when pressed, the tone automatically sets to "000 St.GrPno" and the rhythm automatically sets to "120 PnoBld 1".

The keyboard itself weighs 5.9 kg and is 960 x 375 x 146 mm. The sockets on the rear of the keyboard consist of a DC 9V adapter socket, a phones/output jack, sustain/assignable jack, and MIDI IN/OUT terminals. In addition to the DC adapter, 6 D-size batteries can also be used to power the keyboard.