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GRM Tools v1.5 & HyperPrism

Mike Collins gets to grips with GRM Tools and compares it to the latest incarnation of Hyperprism.

GRM Tools is a set of sound‑processing and synthesis algorithms operating in real time with Digidesign cards on the Mac. It was designed and developed by the Groupe de Recherches Musicales of the Institut National de l'Audiovisuel (Paris) by Hugues Vinet, based on 15 years of research and development. This sounds like it should be hot stuff — so let's see...

The GRM Tools package was developed using Apple's HyperCard software, so it employs a number of different 'cards' on screen to control each algorithm. Fourteen algorithms are provided, offering everything from time‑stretching to Doppler effects and various unusual time‑based signal processing algorithms. GRM Tools was initially developed as a set of experimental tools for composers, but will be of interest to any musician or producer looking for new tone colours or transformation effects.

System Requirements & Facilities

If you have a suitable interface with your Digidesign hardware, you can work with direct inputs, either analogue or digital, to record and play audio files in SDII format. Version 1.5 of GRM Tools supports Sound Accelerator II, Audiomedia II, and Pro Tools cards. You can use the earlier Sound Accelerator I Rev A and Rev B cards, but only if you fit extra memory chips. The Rev A cards need six Cypress CY7C198 45PC RAM chips, and the Rev B cards need three Cypress CY7C198 45PC and three Cypress CY7C199 45PC RAM chips — these can be supplied via Digital Music Archives. Of course, you also need a 680x0‑based Macintosh with a free NuBus connector, and at least 8Mb of RAM!

A specific set of algorithms has been developed and optimised for each of the different Digidesign cards. For instance, the equaliser offers 14 filters on the Audiomedia II, but has 23 with Pro Tools and Sound Accelerator II. The early Sound Accelerator I card is mostly monophonic, the Sound Accelerator II and Audiomedia II cards are stereophonic, and some real‑time quadraphonic uses are offered with the Pro Tools card. The software can handle up to 24‑bit files, and simultaneous playback and recording are possible in stereophonic mode, except in some cases with the Sound Accelerator I. The sound sources may be either real‑time inputs (analogue or digital, depending on the interface you're using), or SDII format files.

Start Me Up

To get started, you first select the Levels algorithm to set the input levels and generate a test signal. Once everything is OK, you can choose from the excellent selection of creative algorithms to process your sound. Algorithms available are:

  • AddSynth (enables you to generate a sound using additive synthesis)
  • Band Pass/Reject Filters
  • Comb Filters
  • Delay Accum (accumulated delays)
  • Doppler effect
  • Equals 23/14/8 (a bank of linear‑phase graphic equalisers, with the number of available bands depending on your hardware)
  • Freq Conversion (a sampling rate converter)
  • Gate Ring (a noise gate)
  • Pitch Accum (harmonisation and re‑injectable delays)
  • Pitch Random (random, oscillator‑controlled pitch transposition)
  • Shuffling (random micro‑splicing)
  • Time Freezing
  • Time Stretching (time compression/expansion with harmonisation).

Using The Tools

The simplest way to get into action is to load the factory settings for your particular Digidesign card using the Menu selection in the Settings Menu. Then you can open a Sound Designer II file using the Open Playfile option in the File Menu, and choose Draw or Show Waveform from the Window Menu to draw the waveform display into a rectangular window. Finally, you choose your algorithm and adjust the available parameters to get the effect you want. Each algorithm has parameters controlled by sliders and buttons, and a Help Mode is provided to give you a brief description of the purpose of each button, control or display.

Once you've determined the desired settings for the algorithms you want to use, you can save these for future use. The Import Settings dialogue box lets you open a second settings file and merge some of its algorithms in the open settings file. If you've selected Enable Keyboard Control from the Settings Menu, you can even load settings 'on the fly' by pressing preset keys on the Mac keyboard. While you're recording audio into GRM Tools you can apply different effects in real time by hitting these keys in turn, to call up different settings. So, for instance, you could apply progressively longer delays, or different EQ settings, or whatever you like.

Most of the algorithms have a bypass button, an input level control which allows up to 12 dB of boost, and a direct level control to set the balance between direct and processed signals. You can click on the displayed values of the slider controls if you want to set the value numerically (with total accuracy) rather than by dragging the slider. There is also a graphic area on many of the algorithm control windows with a button which you can drag around to set the values of one or more parameters.

The different cards have different amounts of RAM available. The Audiomedia II card has enough RAM to hold 92.8ms of audio at 44.1kHz, the Pro Tools and Sound Accelerator II cards can hold 371ms of audio in RAM, and the older Sound Accelerator I card with extended RAM can hold up to 743ms of audio. The reverb time can actually be set as long as 10 seconds on a Sound Accelerator I card with extra RAM fitted, which gives this setup an advantage in this respect. More memory also offers extended possibilites for algorithms which provide delays — so, for instance, the old Sound Accelerator I card again offers the most elaborate algorithms in terms of feedback.

When you use a sample file as a sound source, this requires more computing power than when you use an external input (microphone on the input palette). Recording in a sample file uses additional computing power. For this reason, simultaneous playback and recording of sound files are not available in some algorithms. One way to get around this is to use sound files in input and record the sound output onto DAT. You also need to bear in mind that more computing power is used at 48kHz than at 44.1kHz. When using a sample file as sound source, you should use internal sync for the hardware interface, as this requires less computing power than the external sync mode.


Richard Gonski of Digital Music Archives commented: "I have recently been working on a couple of compositions where I have used a vocalist on one and a violinist on the other, and have recorded them to DAT improvising through GRM Tools with the comb filter and other effects. Then I take these into GRM Tools and Turbosynth to create a range of processed audio files, which I can edit using Pro Tools, to incorporate into my compositions. I feel that GRM Tools gives me just the quality of sound that I'm looking for, where the filters process the sound extremely cleanly, giving a 'digital' sharpness and brightness which I find works very well." So real‑time processing of sounds is one area where GRM Tools is particularly strong. You can regard the software as a sophisticated effects processor through which you can feed 'live' audio, or via which you can process existing material.

To sum up, I believe that GRM Tools is an indispensable set of software 'tools' for creative sound processing, which anyone involved in creating special effects for records, films, video or radio will be interested in. I would like to see this software available as a plug‑in for all the different MIDI and audio packages I use, such as Sound Designer II, Pro Tools, Studio Vision, Premiere, and so forth. Coming in the next software revision, which is due in about three months, will be several new algorithms, plus MIDI control of various parameters. Meanwhile, I'll just have to be content with using version 1.5 — which I have already been able to put to good use creating special sound effects for a multimedia project.

Grm Tools £400prosUseful set of processing algorithms.Detailed parameter controls.Both graphical and numeric controls.consNo MIDI control yet.Algorithm naming scheme could be better.More algorithms would be welcome.summaryGRM Tools offers a professional and versatile set of processing tools for digital audio which no serious sound designer ought to be without.

GRM Tools £400.

Hyperprism Version 1.1

Edgar Varese spoke about his 1923 composition 'Hyperprism' using these words: "The universe of possible musical forms is as unlimited as the number of external forms of crystals."

Georges Jaroslaw, a French musician and composer, was inspired by these words to design Hyperprism for the Macintosh — a highly flexible, real‑time effects processor which lets you 'play' effects in real time. Hyperprism offers interactive graphical control of up to two effect parameters in real time. You move a pointer within the screen to trace out a path, thus changing parameters according to the pointer's position along this path. The centre point of the screen is the position of no change, and any other point you choose applies changes to two parameters of whichever effect algorithm you are using. If you simply wanted to apply a static effect, you would click the mouse button once to set a particular point on the screen, which would apply the effect parameters of your choosing. Drawing a path on‑screen provides for more interesting dynamic (moving) changes to the sound. HyperPrism has quite a bit in common with GRM Tools, but is sufficiently different that it makes sense to consider buying both of these programs if you're serious about sound design.

The software has plenty of features which make it a pleasure to use. You can use two effects simultaneously — one fixed delay and one time‑varying effect. Multi‑pass processing lets you apply any number of effects to a single sound file. The software uses non‑destructive processing, so your original sound files are always safe. The Thru mode lets you process 'live' sounds — with no limits on the duration of the sounds. A couple of functions in the File Menu let you analyse the pitch or the envelope of any sound file, and then use these pitch or envelope settings to process any other file, using the Pitch Follower and Envelope Follower processing algorithms. HyperPrism will not only work with all the Digidesign cards, but, interestingly for some, with the RasterOps MediaTime card also.

So far, well‑known users who have bought the software include Lucas Film, Hanna Barbera, Brian Eno, and the Yellow Magic Orchestra. Clearly this software is of interest to people working with sound for films and cartoons, or in more experimental areas of music. I've heard an advert on TV recently which sounds exactly as though the audio has been processed using HyperPrism, and, if not, HyperPrism would have been the idea tool to use! The playback speed (and hence the pitch centre) of the audio is moving in time as the advert plays — an effect which could easily be created with HyperPrism's Pitch Time Changer. Another example would be using the Multi Delay effect on a gunshot to quickly create the sounds of a shoot‑out.

Hyperprism is the perfect partner for the creative sound designer, composer or musician. The intuitive graphic interface simply invites creativity, especially for those who feel less at home with numbers. I found HyperPrism a joy to use, and will use it from now on alongside GRM Tools to augment my sound effects software.

Newsflash! Hyperprism 1.5

HyperPrism 1.5 arrived just as this review was being finalised, and I was able to look at it briefly. New features include eight new spatial processors, including Quasi Stereo, M‑S Matrix, Stereo Tremolo, Sweeping Pan, and other 'goodies'. Typical functions include mono to stereo conversion, stereo image widening, surround field processing, and more radical transformations which simultaneously pan, phase invert, and filter the input sound according to curves you draw on the screen.

Hyperprism now functions in real time in the background, as you work with other applications in the foreground. There are also various user‑interface enhancements — so, for instance, you can now use the arrow keys on your Mac keyboard to nudge the position of the tracer by one pixel in any direction. MIDI control is now implemented, which lets you either set fixed positions or trace gestures in the Blue Window plane from any MIDI source. This is a feature which many users have been requesting, and is a very welcome addition.

But perhaps the most important new feature for me is the new Hyperprism Consoles. These offer a set of alternative graphic interfaces to Hyperprism, featuring faders, buttons, timers, numerical displays, and a music keyboard, specialised for audio and musical applications.

The Consoles were written using Opcode's MAX, and are made available as a stand‑alone application. This application communicates with Hyperprism using the OMS IAC (Inter Application Communication) Driver, so you need to install this software as well.

MAX programmers will be able to create customised modules of their own for Hyperprism using the rich set of features available in the commercially‑available version of MAX. The Consoles give certain processes a more classical and convenient interface, as an alternative to the Blue Window. For example, the Consoles include Filters (logarithmic progression), Time Stretch (automatic positioning in the Blue Window using a multi‑purpose duration calculator), Pitch Shift (using a keyboard‑like interface accurate to the cent) and Doppler (to ensure steady motion of the tracer). And thanks to MIDI Time Code, any Hyperprism Process can now be triggered to start and stop in sync with a film or video track.

This combination of control options and new features now takes HyperPrism into the lead for me compared with GRM Tools.

Hyperprism £411prosMIDI Control features now available.Wide selection of useful algorithmsAttractively designed, intuitive interface.consAlternative graphical and numerical controls only available via the separate consoles software.summaryHyperprism has the sexier interface, and is indispensable if you prefer to experiment more intuitively with your soundfiles.

Hyperprism £411 inc VAT.