BitHeadz Retro AS-1
An essential synth for any Mac musician

by Rob Albertson
Special to Creative Mac

Ask any musician that grew up in the '60s what some of their favorite sounds were from the era, and the words Moog, Oberheim, and Arp are bound to come up. Despite all the wiz-bang technology of today, the fact is we still can't digitally replicate those huge-sounding analog keyboards of yesteryear. The geniuses at BitHeadz have satisfied this insatiable aural jones with Retro AS-1, a software virtual synthesizer that emulates sounds from the analog era. (The only thing you won't miss is the hernia from carrying one of those monsters around!) Not only is Retro AS-1 ground-breaking in terms of sound and price, it's also revolutionary in that these sounds are all coming from your computer. No more patch cords, drawings of patches, out of tune oscillators, etc. All you need is a fairly robust Mac or PC and a healthy amount of RAM, and you're ready to be the next Herbie Hancock!

When you purchase a digital keyboard these days, you're essentially buying a micro-computer that controls sounds, effects, sound envelopes, etc., housed in a keyboard body controlling the pitch. Because of MIDI, oftentimes musicians will only have one or two keyboard "controllers," and the rest of their sounds will be in the form of rack modules that contain everything but the keys themselves. Retro AS-1 takes your already existing computer and uses the processing power, RAM and interface to turn it into a digital emulation of the classic analog synthesizers.

Features abound
Retro AS-1 features 16-bit, 44.1 KHz sound quality, real-time play response time, full MIDI control and the ability to write synthesizer output to disk in a variety of common audio file formats (8-, 16-, or 24-bit). The programs/sounds are also 100 percent programmable, with more than 100 parameters per sound with up to 200 values per parameter. Essentially you have an unlimited amount of presets, and the disc ships with more than 1,000 factory presets. I found these presets to be an excellent starting point to analog synthesis in general and programming this software in particular. Polyphony is dependent on CPU speed, which can also affect some MIDI applications; the output is stereo.

Retro AS-1's Mixer interface. Click image to enlarge.

The major building blocks of analog synthesis are oscillators (sound source), filters (timbre) and modulation (changing a waveform over time). Retro AS-1 contains three oscillators per voice, an eight-octave range per oscillator, nine waveform types (Saw, Pulse, Triangle, Sine, Sine squared, Glottal and white, pink and red Noise) and the ability to have frequency modulate any oscillator. The filter section has two assignable filters per voice, 13 filter types (including four-pole resonant lowpass, highpass, bandpass and others), multiple inputs allowing parallel and/or serial filtering and the ability to modulate any filter by any oscillator. Modulation parameters include dozens of modulation routings, dozens of low frequency oscillators, six different LFO shapes and even the capability of synchronizing LFOs to MIDI clock. Up to four MIDI controller modulation sources are available simultaneously.

Installation and troubleshooting
So far we certainly have a very deep analog model to work with. Retro AS-1 goes the extra mile by including two serial effects processors per voice, two global effects processors and two global effects sends per MIDI channel. Effects include parametric and shelving equalization, multiple stereo reverb, stereo delays, chorus, phaser, flange, overdrive and distortion effects. Delay times can be synchronized to MIDI clock, and there's even an arpeggiator that can also be synchronized to MIDI clock. The MIDI processor enables full control of layers and splits, 16 simultaneous MIDI channels and a serial port application for direct MIDI input (Mac OS only). System requirements are 32 MB of RAM, CD-ROM drive, 120 MHz or faster PowerPC processor, OS 7.6.1 or higher (OS 8 or above recommended) and 40 MB free hard disc space. Reality check: the faster your processor and the more RAM you have will heavily effect the performance of this program—So what else is new?

Installation of the program was fairly painless. I say "fairly" because to use Retro AS-1 with your sequencer application you have to configure three programs. For my setup I had to install Retro AS-1 (no worries) and then go into OMS and create a new MIDI studio setup—OMS recognized the program but wouldn't play it in the sequencer—and finally have Pro Tools 5.0 reconfigured to allow recording and playback. Once everything was configured properly the program worked fine. I hesitate to mention the installation headaches in this review because Retro AS-1 installed fine; it was really OMS that seemed to be the problem. In fact, the 200-plus page manual ( a .pdf file on the CD-ROM) does a good job of troubleshooting every kind of possible MIDI scenario.

There are three main applications in the Retro directory: Keyboard, Editor and Mixer. Also included are a programs file and a MIDI processor setups file. I did find it a bit confusing that the all of these applications are separate files in one suite rather than one large program. It would be easier to multitask if everything were in one window with the various menus at your disposal rather than opening and closing programs, particularly when you're using the synthesizer with another sequencing program. This is one of the few drawbacks to Retro.

Under any of the three main applications you find Retro's control panel. Here you can customize the basic configuration of the synthesizer's number of voices, maximum CPU usage, sample rate and buffer length. It's a good idea to experiment with different settings in the control panel to find what works best with your system. A slower processor will be limited in how many notes it can play at once. Buffer length will also effect how much data is bussed to Sound Manager. Lower values increase sound quality but decrease polyphony. Other factors include applications you are running and the bus speed of your motherboard. Using a G4 400 MHz Mac with 192 MB of RAM, I experienced no problems. Considering I saw an Arp 2600 the other day being sold on an auction site for more than $2,000, the extra expense in RAM to use this program while other applications are running is well worth it.

Working in Retro AS-1
Once Retro AS-1 is installed into the computer you treat it exactly like a hardware synthesizer. You input and output data on a track and the sound you have selected will play back. You can use the synth on all 16 channels providing a full multitimbral sequence. The more channels you use will influence polyphony, depending on how many notes or chords are on the various tracks. (This is something that all synthesizers have as a limitation, whether or not they're hardware- or software-based). Depending on your sequencer application, you have the ability to name programs and control all of the parameters via MIDI and NRPNs. NRPNs ("nonregistered parameter numbers") allow you to control each program on a specific MIDI channel basis rather than a system-exclusive data dump. You can use Sys-ex commands to control global settings of volume, panning and balance and global effects. I didn't experience much latency in the reaction of the sounds coming from the synth while sequencing, a common problem with other software synthesizers. Latency will be more apparent depending on the programming applications you are running simultaneously. It's probably best to perform intensive programming offline and then save it as a separate program rather than playing the program from the sequencer and trying to control all parameters via MIDI on all 16 channels.

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