This full-size stereo keyboard is of the TONE BANK variety,meaning that it stores more than the standard 127 MIDI complement of sounds (220). It is not touch sensitive but the overall sound is crystal and has some oddities among the usual draft of pianos,brasses,woodwind and strings. There is an on board rhythm machine and one demo song and the ability to memorise one complete recording.There is a 4 level reverb unit (680 only) which,similarly to the CTK series adds life to otherwise dry sounds.
Similar models are CT-670 and CT470. The 470 lacks the reverb unit,the seperate output jacks,using a mini jack for headphones.There is no tuning knob on the 470 and no pitch bend,although it does respond to pitch bend. Oddly the batteries seem to insert in the opposite direction.
The keyboard can be split at the lower half of the keyboard,as is usual on Casio keyboard by selection of one of the two modes for chord accompaniment. Once selected the various parts of the backing can be switched on or off as desired - only the bass has not got a switch to remove it from the accompaniment. The CHORD1,CHORD2 and OBBLIGATO sections having each a button to remove them. The obbligato section follows the chord vamping of the selected chord. Other functions included for the lower half of the keyboard are HARMONIZE and ECHO LINE. The first forms an added harmony to the upper melody according to the accompaniment chord. The latter is a rather quirky feature which attempts to base an added melody line played behind the one just played on the upper manual.
The upper manual sounds are switched by banks - in a rather odd way compared to more modern keyboards. Pressing one of the numbered keys selects the sound with that number and this selects the main sounds 0-9,the "select" button then chooses those marked 10-19. The Tone Bank switch then adds a decimal digit adding further variations to the main group of sounds resulting in the 220 tone bank.
The CT-680 does not store internal user sounds,but if you think you are stuck with the manufacturer's sounds then don't worry - there are 4 parameters you can alter for the main tone : DETUNE,DELAY,ATTACK/DECAY,RELEASE. The detune control will add an enharmonic tone or a harmonic tone depending on how far you detune.The delay causes the sound on the right speaker to follow the initial sound after a period of time,which causes a kind of echo effect.
The attack/decay and release controls control the initial and final phases of the volume envelope shape - meaning you can slow the initial rise in volume of something like a piano to be more like a violin,or with use of the release control,sharply halting electronic pianos can be made to last longer for sustain effects.
There are also SUSTAIN and VOLUME jacks at the rear for pedal and switch controls over the sound. In addition to the headphone stereo jack there are also left and right LINE OUT jacks. A tune control is also at the rear to tune the unit to existing instruments.
The rhythms are switched in the same BANK way as the sounds,though with only 110- MIDI should be able to cope without bank switching. The patterns cover the usual array,but with some rather more modern additions,such as Hip-Hop and Techno,though these are no way near as good as the Yamaha DJX. The bass and snare drums are quite deep and powerful PCM noises and the result is quite pounding through the on board speakers,moreso than some of the smaller MT series PCM keyboards.
The Rhythm controls are rubberised keys as opposed to the hard plastic selectors elsewhere - but the overall tactile feel is of something that should keep working without fail.There are two INTRO keys (long and short) as well as a BREAK,FILL-IN and ENDING as well as CODA button. Tempo is adjusted via an up and down button and pressing both defaults the tempo to normal for that beat.
Synchro mode starts the drums upon playing the manual keyboard.
The MIDI functions are rather none-standard and need some explaining,especially considering the PDF download document seems only available in Spanish. There are IN,OUT and THRU sockets,but how the data is sent and received depends on the mode that it happens to be in.The manual refers to MODE A and MODE B. Upon switching the CHORD/MIDI switch to "MIDI" the keyboard is in MODE A and receives data as a solo instrument. The Chord1 & 2,Obbligato,Harmonize,and Echo Line buttons then become controls for the channels upon which the CT-680 recieves. The arrangement is similar to the CZ230s and MT540 having 4 channels which the keyboard recieves on - 4 being for the rhythms - but as the drums start on patch 12 (not MIDI prg 12!) it is possible to have more than one channel with drums on. The last switch (Echo Line) is used to determine external or internal clock pulse mode to synchronise to other drum machines. This arrangement is not good for those machines whose drum channel is 16 or 10. The pitch bend (from the on board control) is sent and responded to.
The awkward thing is that because the CT has 220 sounds - getting all of them under MIDI control requires bank switching - usually this is done with the bank switch command - but not here! The CT-680 uses System Exclusive to do this - which is about as stupid as it could be- this is what I found on the internet: (and later proved to be true)
Q. I need to do bank switching on a Casio CT-670 keyboard or on older MIDI equipment via MIDI in order to get past the 128 instrument barrier. How do I do this?
A. Well, you may need to use a SYSTEM EXCLUSIVE command. This is applicable only via a sequencer or patch librarian. The command for the Casio CT-670 keyboard is the following:
F0 44 03 00 C 51 X F7 -- where N is 70 for channel 1, 71 for channel 2, and so forth, and where X is 20 for bank 0, 21 for bank 1. Note that these are in hex. The decimal equivalent is the following:
240 068 003 000 C 81 X 247 -- where C=111+channel number (1-4) and where X is 32 for bank 0, 33 for bank 1.
Be aware that these commands MAY work with Casio CT-680 keyboard. WARNING: BE SURE TO ISSUE A PROGRAM CHANGE BETWEEN 0 TO 9 BEFORE ISSUING THIS SYSTEM EXCLUSIVE COMMAND, OR OTHERWISE STRANGE BEHAVIOR MAY RESULT. IN ADDITION, YOU SHOULD USE A NUMBER THAT IS EQUAL TO THE SECOND DIGIT OF THE DESIRED
INSTRUMENT NUMBER. For example, if you want to use program #56 or #156, use the following command sequence:
SE F0 44 03 00 70 51 21 F7 (replace ‘21’ with ‘20’ if you want program #56.)
Please note that I do NOT know the system exclusive commands for other models of MIDI equipment. There IS a way that you can find out how to do bank switching on other equipment. Hook the MIDI OUT of the device in question to a sequencer and record yourself doing a bank change. Now go into the sequencer and examine the event list if it has one. Good sequencers have this.
As above - I plugged the CT-680 into MIDI-ox (free from the internet) and found it did exactly the above - which is not much use unless your sequencer can add SYSx commands to its data stream. (Cakewalk can - so use that!)
Good Points: The tactile feel of all the controls is durable and the quality of the PCM sounds with reverb is impressive. The large keys respond well and are damped and have a long travel - playability is therefore good. The reverb enhances the sounds no -end and the drums are punchy and useable,sounding less "toy" than MT series PCM drums. The stereo effect of the keyboard is well used as when a delay is introduced or when some of the layered or split sounds are chosen,instruments sound from either speaker.
The 680 features separate left and right output jacks as well as a headphone jack,and a swell pedal control.
Niggles: The size of the case is more than is necessary since there is a plastic rim around the outside which is aesthetic only and adds to the cumbersome size,which isn't the case with the 470. The annoying bank switch method using system exclusive is ludicrous, considering MIDI is a standard and this is as none-standard as is possible. Pitch bend is fixed and not programmable but this is minor issue