Page  311 ï~~The University of Texas Accelerando Project: An Update Russell Pinkston Department of Music The University of Texas at Austin Austin, Texas 78712 ABSTRACT An enhanced version of the Accelerando Box1 has been completed and is now commercially available from White Instruments, Inc. The new model utilizes the 27MHz Motorola 56001 and can be equipped with stereo 18-bit A/D and quad 20-bit D/A converters and up to 4 MWords dynamic RAM. Music56000, the DSP synthesis language written for the Accelerando Box, has been modified to support the new hardware and its MIDI implementation extended. The Patchwork symbolic compiler, originally developed for the Apple Macintosh and IBM PC under Microsoft Windows, has now been ported to the Silicon Graphics Indigo under X-Windows, specifically as a front end to CSound. 1. THE ENHANCED ACCELERANDO BOX New Hardware Design The original Accelerando Box has been described in detail elsewhere 1, but it basically consisted of a 20MHz Motorola 56001 DSP, 32K of static RAM, MIDI in/out, a Yamaha Digital Cascade interface, and an IBM-compatible 8-bit bidirectional parallel port. It was designed to function as a real-time digital audio signal processor which was fully programmable and capable of being controlled either by MIDI or from a host computer via the parallel port. The main idea behind that design was to create a general-purpose DSP module which could be directly attached to an IBM PC and/or operate in stand-alone mode, as a conventional MIDI device. It could also be daisy-chained with an unlimited number of similar modules using its MIDI and digital audio interfaces. The original box did not have Digital/Analog conversion hardware, but relied on Yamaha Digital Processors (e.g, DEQ7, DMP7, etc.) for analog input and output. Accelerando II incorporates many aspects of the old design, but it uses the 27MHz 56001 and abandons the Yamaha Digital Cascade in favor of the more widely-used AES/EBU digital audio interface. It also has Direct Digital I/O ports for daisy-chaining multiple boxes and to provide direct access to the 5600l's SSI and SCI ports. (With an appropriate adapter cable, this would also allow the box to be connected to a NeXT computer via its DSP port.) The most important new feature of the Accelerando Box, however, is that it can now be equipped with up to 4 MWords of Dynamic RAM, as well as stereo 18-bit A/D and quad 20-bit D/A converters. The analog inputs/outputs use balanced, XLR connectors, there is 2K of EEROM for saving programs and parameter settings, and there is also an LCD display and programmable push-button editing controls on the front panel. The device is currently being manufactured and sold by White Instruments, Inc., of Austin, Texas, as part of their 5000-series of DSP devices. New DSP Software The MUSIC56000 synthesis language has been revised to accomodate the new hardware and a number of enhancements have been made, especially in the area of MID! support. All types of incoming MID!I messages are now accessible for use as realtime controls, and a set of MIDI processing and output units is planned. There are also several new macros which allow the user to take advantage of the LCD display and front panel controls, others which facilitate host communications via the parallel port. Audio rate calculations are now performed on an interrupt-driven basis, so that all other operations (including MIDI processing) can be handled in the main program loop, as a background task. Consequently, the box can be used for both audio and MID! processing at the same time..311

Page  312 ï~~Several other extensions to MUSIC56000 are currently being developed, which take advantage of the large amount of dynamic RAM and quad D/A converters available on the new boxes. Specifically, macros are being written for sampling, loop editing, and playback, as well as for quadriphonic room simulation and the simulation of moving sounds. A set of standard studio effects and demonstration synthesis designs are also being assembled, which will be included with the Accelerando Box when it is shipped. New Host Software The primary platform for the Accelerando host software continues to be the IBM PC, since the standard printer port can be used for high speed digital audio transfers to/from the Box. In addition to the in View digital audio editor and the Patchwork symbolic compiler, which have been described elsewhere, a comprehensive loader and control program for the Accelerando Box has now been written, which also runs under Microsoft Windows. The control program can communicate with the Box using either the parallel port or a Roland MPU401-compatible MIDI interface. It allows the user to load a DSP program to the Box, and then control it using a variety of graphical objects (a keyboard, slide faders, edit boxes, etc.). There is a template editor provided, so that custom edit/control panels can be designed to support any desired algorithm running on the Accelerando Box. These panels, along with different sets of parameters, can then be saved for future use. Finally, standard MIDI files can be played from disk, with the output directed to either the MIDI or parallel port or both. [fzm *@SQTIZ sqrt _ _ _ _ _ _ _ _ _ _ _ _ sqrt A simple quadpanning,instrument inPatchwork, showing the use of MIDI continuous controllers and the front panel LCD of the Accelerando Box for VU meter. Note that MIDI continuous controllers are converted to real values between +/- I by the Accelerando MIDI handler. 312

Page  313 ï~~2. PATCHWORK ON THE IRIS INDIGO Keith Lent's Patchwork program, initially developed on the Apple Macintosh, then implemented on the IBM PC and the NeXT computer, has now been ported to X-Windows on the Silicon Graphics IRIS Indigo workstation, using OSF/Motif. X-Patchwork is optimized for use as a graphical front end to MIT's Csound, which is capable of running in real time on the Indigo. It includes a number of enhancements over previous versions of Patchwork, including multiple wire types (for CSound's a, i, and k-variable names), multiple code lines per device icon, and several new compile options, including one which compiles the drawing, runs CSound with either MIDI input or a user-written test score, and then plays the output sound file, if one has been generated. 3. ACKNOWLEDGMENTS This research was partially funded by the University Research Institute of The University of Texas at Austin, and was also supported by a number of corporations, including Motorola, Silicon Graphics, and White Instruments, Inc. The enhanced Accelerando Box was co-designed by Keith Lent, Peter Silsbee, and Rick Bocock (Chief Engineer for White Instruments); Keith Lent was the principal DSP software architect. I also wish to thank the following students at The University of Texas at Austin for their contributions: Bill Morgan (Computer Science) performed the port of Patchwork to X-Windows, which involved a virtually complete rewrite of the program. Stephen Carl (Computer Science) is developing host software under Microsoft Windows, Turker Kuyel (Electrical Engineering) is designing the MUSIC56000 tools for quadriphonic room simulation and moving sounds, and Michael Duffy (Electrical Engineering) is implementing the Accelerando Sampler. 4. REFERENCES 1. Lent, Pinkston, and Silsbee. 1989. "Accelerando: A Real-Time, General Purpose Computer Music System," Computer Music Journal, 13(4): 54-64. 313