Programming Manual: Glossary
BOARD — A board consists of a pair of CHANNELS. The system contains eight boards, and each board is independent of the other boards. That is, the sounds produced by each board has nothing to do with, and no effect on, the sounds produced by the other boards. Each board has two OSCILLATORs, two WAVESHAPERs, two FILTERs and two VOLUME CONTROLs, all implemented as conventional analog synthesizer circuitry. Each board also includes two GLIDE generators, two SWEEP generators and four ENVELOPE generators, all of which are implemented as computer software processes, not as analog hardware.
CHANNEL — A channel consists of an OSCILLATOR, a WAVESHAPER, a FILTER and a VOLUME CONTROL, supported by a GLIDE generator, a SWEEP generator and two ENVELOPE generators. Often, channels are paired for greater tonal complexity. See BOARD.
CURRENT PROGRAM — In addition to the fifty stored PROGRAMs in the Chroma's memory, there is the current program, sometimes called Program 0. This program always controls the sound of the synthesizer (or of the main INSTRUMENT when LINKING). In addition, the programming controls function on the current program, not on the fifty stored programs. This means that the current program is a form of workspace in which all programming is done. If the programmer wishes to keep a sound he has created for future use, he must use the Store switch to store the current program into one of the fifty positions in the Chroma's memory. In order to listen to one of the stored programs, it is necessary to select the program, which actually causes the stored program to be copied into the current program space. Even though the current program is not considered a "stored" program, it does reside in the Chroma's battery back-up memory. This means that the instrument can be turned off today and then turned on tomorrow and the current program will be remembered, along with the fifty stored programs.
EDIT MODE — Since the CHANNELs in the Chroma are often used in pairs, two complete sets of parameters are required to completely define the sound of an INSTRUMENT. These are the A PARAMETERs (which are used even when the channels are not paired) and the B PARAMETERs (which are only used when the channels are paired). In order to access these two sets of parameters (without having another fifty switches on the panel) the two edit mode switches are provided. In Edit A mode, the display and parameter control slider are connected to the A parameter. In Edit B mode, the display and slider are connected to the B parameter. In Edit A & B mode (entered by pressing both edit switches at the same time), the display will show the A parameter's value, yet as soon as the slider is moved both the A and B parameter will be set to the value determined by the slider position. Since the edit mode and (parameter) number is itself a PANEL PARAMETER in the CURRENT PROGRAM, the edit mode and number can be stored so that the slider is automatically connected to a particular parameter whenever a particular program is selected.
ENVELOPE — Any aspect of a musical tone, such as its pitch or its volume, can be described in quantitative terms. One can say that a tone's pitch is middle C and its volume is -15dB, or whatever. However, if an aspect of the sound varies with time, it's not that simple. Fortunately, the time-variations of an aspect of a tone can often be reduced to a simple patttern or combination of patterns. An envelope is one of these types of patterns. In many synthesizers, envelopes are of the type called ADSR, for Attack Decay Sustain Release, which are the four PARAMETERs that describe the shape of the envelope. In the Chroma, this has been simplified to ADR, meaning that each envelope has an ATTACK time, a DECAY time and a RELEASE time. In addition, each envelope can be made larger or smaller in magnitude in response to how hard the key that triggers it is struck. When a key is pressed, the computer inside the Chroma decides which CHANNEL(s) will be used for the note, and then sets the envelopes for those channels to their attack phase. The envelope generators will then proceed to generate their programmed shape, consisting of a rising attack and a falling decay, until the key is released, at which time the envelope generator will be forced to generate a falling release, which is similar to decay, yet usually faster. The shape of the envelope by itself does not produce any sound, yet it can be used to dynamically modulate aspects of the sound such as volume or filter cutoff.
GLIDE — Most synthesizers have provisions for causing the pitch of an oscillator to slide from one note to the next, and in most synthesizers, this function is called PORTAMENTO. The Chroma, however, uses what is called a glide generator, which is capable of generating PORTAMENTOs (smooth slides) and GLISSANDOs (chromatic runs).
GLISSANDO — The GLIDE generators in the Chroma are capable of causing the transitions from one note to the next to be done by a series of chromatic steps. This is called Glissando. A wide range of glissando rates is available.
INSTRUMENT — Although the Chroma is, of course, a musical instrument, the term "instrument" is used here to refer to that group of BOARDs and PARAMETERs that causes the Chroma to create a particular sound. The Chroma is capable of creating two different sounds at once by LINKING, or eight at once using the computer interface. Therefore, from the programmer's point of view, the Chroma can be thought of as containing several "instruments," and though they do not have discrete physical identities (they are all inside the same box), they have distinct identities as data structures.
KEYBOARD SPLIT — When usig the LINKING feature, it is possible to make the Chroma function as two INSTRUMENTs at the same time. If link lower or link upper mode is selected, the keyboard split will determine which keys control which instrument. Since the keyboard split is a PANEL PARAMETER, it need not be set up every time a link is set up. Rather, it can be stored along with the link information and all the other parameters, and automatically set up whenever the appropriate program is selected. However, it can be altered quickly using the Set Split switch.
LINKING — Normally, the Chroma functions as a single INSTRUMENT, whose sound is defined by the CURRENT PROGRAM. To enhance the versatility of the instrument, there is a special PANEL PARAMETER that is accessible from the control panel that allows the Chroma to function as two instruments. In this mode, the main instrument is still controlled by the current program, while the link instrument is controlled by one of the fifty stored programs. The stored program that controls the sound of the link instrument cannot be directly accessed by the programmer without selecting that program (making it the current program). The link feature has four modes, no link, link lower, link unison and link upper. In no link mode, the linking feature is not used. In link lower mode, keys below the KEYBOARD SPLIT cause the link instrument to sound and keys above or equal to the split cause the main instrument to sound. In link unison mode, each key will cause both instruments to sound, which of course reduces the apparent number of VOICEs available, yet produces extremely rich sounds. In link upper mode, keys above or equal to the keyboard split cause the link instrument to sound while keys below the split cause the main instrument to sound. The linking can be quickly set up from the panel (see TWO PROGRAM LINKAGE Switches) [changed from "CHROMA SWITCH DESCRIPTIONS" in the original manual]. In addition, since the link mode and number is in fact a PARAMETER within the CURRENT PROGRAM, the link can be stored so that it will automatically be set up whenever the program containing the link is selected.
MODIFIED FLAG — Since the CURRENT PROGRAM is only a copy of one of the stored programs, and since the current program can be modified, independently of the stored program, by the programming controls, an indication of whether or not the current program equals the stored program is shown at all times. The units decimal point in the large two-digit display is used for this purpose. Whenever a program is selected or stored, the program number display will be set to the appropriate number and the modified flag will be turned off. Whenever the current program is changed, the modified flag will be turned on, telling the user that what he is hearing (as controlled by the current program) is not the same as what is in the Chroma's memory (in the stored program). Note that, since the parameter number, edit mode, link, etc., are all parameters, changing any of these will set the modified flag.
PANEL MODE — The Chroma's control panel can operate in four basic modes. The mode determines the function performed when one of the fifty numbered switches on the right side of the panel is depressed. The mode used most often during performance is the Program Select mode. In this mode, depressing one of the fifty swiches on the right panel will copy an entire PROGRAM into the CURRENT PROGRAM, and also set up the PANEL PARAMETERs and establish any LINKING specified by the program. The mode used most often during programming is Parameter Select mode. In this mode, depressing one of the fifty switches selects one of the CONTROL PARAMETERs or, depending on the EDIT MODE, either one of the A PARAMETERs or one of the B PARAMETERs. When a parameter is selected, its number and value are shown in the eight-digit display. In addition, moving the PARAMETER CONTROL SLIDER causes the value of the parameter to change to whatever the programmer wishes. The remaining two modes are called Copy From A and Copy From B. In these modes, depressing switches on the right panel causes the appropriate parameter to be selected, and copies its value from a program whose number was selected when the Copy mode was first entered. The panel mode (including the program number being copied from the Copy modes) is stored in the battery-backup memory so that the instrument will always power up in the same state it was when it was last shut off.
PANEL PARAMETER — there are six panel parameters in each program. They do not directly affect the sound created by the INSTRUMENTs. Rather, they are extra parameters that automatically initialize certain things that are accessible from the control panel. The panel parameters include the Link Balance, the Link Mode & Number, the Edit Mode & Number, the Main Transpose, the Link Transpose and the Keyboard Split. Although these panels parameters do end up affecting the sound, they do so by other means than by altering the INSTRUMENT that is creating the sound. For instance, the Main Transpose transposes the notes that are played on the keyboard before they are given to the main instrument process inside the computer. The part of the computer that generates the sound does not know (and does not care) whether you play middle C with no transpose or low C while transposed up 1 octave.
PARAMETER — A Parameter is a single numerical quantity that controls one specific aspect of the operation of the Chroma, usually an aspect of the sound that is being created. Each parameter has a number that identifies what it controls, and a value that specifies the setting for the particular control. For instance, filter tuning is parameter number 39, and it has a value that can range from 0 to 63, representing tunings that span the entire audio spectrum in whole-tone increments. This particular parameter represents the tuning of the filters that it controls before any modulation is added to the tuning. For a complete list of parameters and what they represent, consult the section entitled TABLE OF PARAMETERS. The parameters fall into four categories, however, called the PANEL PARAMETERs, the CONTROL PARAMETERS, the A PARAMETERs, and the B PARAMETERs [see PANEL MODE], all defined elsewhere in this glossary.
PATTERN — The SWEEP is capable of generating typical LFO waveshapes such as sine, square, triangle, etc. In addition, it is capable of generating stepped patterns. These patterns consist of a short sequence of values that repeats at a regular rate. In fact, the square wave that the sweep generates is actually a two-state pattern. There is also a random "pattern" that sounds like a conventional synthesizer with noise feeding a sample & hold.
PROGRAM — A program is a set of PARAMETERs used to describe the sound that will be created by the Chroma (or, more precisely, by an INSTRUMENT within the Chroma). There are 101 parameters in each program, most of which directly control the sound. The Chroma's memory is large enough to contain 50 stored programs, plus one "current program," which is the program that is currently controlling the synthesizer and is accessible to the programmer. Programs can be moved around the Chroma's memory by SELECTING or by STORING. A secondary program can be called upon, in order to get to sounds at a time, by LINKING programs.
SWEEP — One of the dynamically varying quantities that can control an aspect of a sound is called the sweep. In other synthesizers, it is often called the LFO, for Low Frequency Oscillator. However, in the Chroma there are not any oscillators for this function. Rather, this control function is generated by the Chroma's computer. So, it is given the term SWEEP instead of LFO. The sweep has several parameters that control its operation, including its rate and its waveshape. Like the ENVELOPEs, the sweep produces no sound of its own, yet can be used to dynamically vary an aspect of the sound being created, such as the volume or pitch.
TEMP MODE — Short for Temporary Panel Mode. In addition to the four PANEL MODEs which determine the function of the right panel switches, there are eight temporary modes, indicated by a blinking LED on the panel, that determine the function to be performed by the next depression of one of the right panel switches. As soon as a right panel switch is pressed, its temporary function will be performed and the temp mode will be cleared, returning the Chroma to its previously set panel mode. In some cases, use of a temp mode will result in the panel mode being changed. The specifics of these modes can be found under the section entitled SWITCH APPENDIX [again, not sure what this is referring to]. The temp mode, like the PANEL MODE, is stored in the Chroma's battery-backup memory, so that the Chroma will always power up in the same state it was when it was last shut off.
VOICE — The term "voice" has several meanings in the synthesizer industry. However, the term has a very specific meaning as far as the Chroma is concerned. A voice is the total sound you hear as a result of pressing one key. The number of voices a synthesizer has is determined by how many tone generators it has (16 in the Chroma) as well as how many tone generators are required for each note (anywhere from 1 to 16 in the Chroma, typically 2). This means that the Chroma can function as a synthesizer that has anywhere from 16 voices down to 1 voice, usually 8, depending how it's programmed. The term "voice" does NOT refer to how many different sounds the instrument can remember. That is the number of PROGRAMs that the synthesizer can store in memory.