User manual LEXICON MPX 1 V1.10 MIDI IMPLEMENTATION DETAILS

[. . . ] MPX 1 V1. 10 MIDI Implementation Details © 1998, Lexicon, Inc. · 3 Oak Park · Bedford MA 01730-1441 · Tel: 781 280-0300 · Fax: 781 280-0490 Lexicon Part No. 070-11835 Rev 1 Printed in U. S. A. Contents Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 Data Formatting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . [. . . ] One approach is to request the Report Effect Parameters (18 hex) message which returns this list directly. A more generic method of generating a list of Parameter Types for a given algorithm is to use the Parameter Type (03 hex) message. The request for this message class takes the control address for a parameter and returns the Parameter Type at that address. For example, "pitch" is at control address 0-0. The pitch algorithm Detune (M) is at address 0-0-1. Detune (M) parameters are at addresses 0-0-1-0 through 0-01-3. The Detune (M) parameter itself will tell you how many parameters it has from which you can request the Parameter Type message for each parameter to build a local list with. Once the Parameter Type number is known, the number of bytes used by the parameter can be derived from the Parameter Description. There are two basic approaches to dealing with Parameter Descriptions. One is to request the Parameter Description (04 hex) each time you have a Parameter Type number and you need to know something about the parameter. The other approach is to build a database of parameter descriptions locally and reference it whenever you need to find out something about a parameter. If disk space and/or RAM space is available, the latter approach is preferable as it makes acquisition of Parameter Descriptions a one time effort. 27 MPX 1 V1. 10 MIDI Implementation Details Lexicon It is important to remember that the MPX 1 allows parameters to have "option" values. "Delay Units" for example, determines the units in which delay time is adjusted (milliseconds, feet, meters, etc. . . ). As "Delays" are stored in their "Unit" values, it is essential to read the options unit value before operating on the actual delay setting. Because of this close association of options to their attached parameters, option data ALWAYS immediately follows the parameter data to which it is associated. In this example, this means that the 2-byte "delay" parameter becomes a 3-byte parameter. Continuing the previous example, to access the "P Dly" parameter, you must get past the "Tune" parameter and it's option parameter value. You will note that, although "Tune" is a 1-byte parameter, its description structure reveals that it has an option: "Optimize". pitch parameter data: 0x64 - Mix 0x00 - Level 0x0A - Tune 0x01 - Tune Option 0x00 - P Dly 0x00 - unused The option parameter itself is identified by a Parameter Type number which we use to access the structure describing it. The "Optimize" Parameter Description indicates that it is a 1 byte parameter so we increment the pointer one last time to get to the "P Dly" parameter data. pitch parameter data: 0x64 - Mix 0x00 - Level 0x0A - Tune 0x01 - Tune Option 0x00 - P Dly 0x00 - unused Note that not all option parameters are 1-byte. These are embedded onto the MSB of the parameter itself. Other values which may appear in the parameter data packet should be ignored. LFOs through Envelopes (Bytes 722-843) The data for the LFOs, Arpeggiator, ADSRs, Random number generator, AB, Sample and Hold and the Envelope Generators are organized in a similar fashion to the effect parameter data. The only difference being that there are not multiple algorithms. [. . . ] Note that if "Link" is turned on, the value is scaled Shape Disp Units Display in decimal Slope Disp Units If the value is < 16, a minus sign is displayed followed by 16 minus the value in decimal. Otherwise, a plus sign is displayed followed by the value minus 16 in decimal Dplevel Disp Units If the value is 0, "Off" is displayed. If the value is the "max_value", "Full" is displayed. Otherwise, a minus sign is displayed, the value is multiplied by 2 and used as an offset into the "levelog_db" table, where the first display value is derived. [. . . ]