If you have never heard of Sonic Foundry's Acid Pro, let me bring you into the loop. Imagine an intuitive paint-and-play remix application, in which any

If you have never heard of Sonic Foundry's Acid Pro, let me bring you into the loop. Imagine an intuitive paint-and-play remix application, in which any slice of music can be imported into a musical project regardless of tempo, pitch, format or taste. Scary as it sounds, Acid Pro has been known to induce instant gratification, legions of sleepy users and plenty of killer remixes. With version 4.0, Sonic Foundry has taken to raising its own bar by improving Acid's MIDI editing (introduced in version 3.0) and project work-flow options, as well as adding a host of new features such as effects automation, crash-guard protection, odd time signatures, VST Instruments, 5.1 surround mixing and ASIO support. Tack on Acid's multiple-format support (like MP3 and multiple-bit WAV/AIFF in the same project) and expansive — but not expensive — loop libraries popping up all over the Net, and Acid Pro is just plain dangerous.

In some ways, Sonic Foundry is playing catch-up with 4.0. For instance, the newly added ASIO support, piano-roll MIDI editing and automated effects hardly seem progressive when compared with the rest of the industry. In versions 2.0 and 3.0, it seemed as though Sonic Foundry was avoiding Steinberg's ASIO driver, ReWire and VST and VSTi technologies and opting for more pedestrian features like the tempo-detecting Beatmapper. Bearing this in mind, no single feature leaps off of Acid Pro 4.0's spec sheet like VSTi compatibility. You've seen those cool little VST soft synths hanging out on the Internet and just waiting to be downloaded and injected into your latest house jam. Yet by the time I scribbled this review's last few edits, VSTi compatibility (see Fig. 1) ranked behind the less-flamboyant but powerful piano-roll MIDI editing, the transparent improvements to Acid's playback engine and the boring but necessary addition of ASIO support. If version 3.0 left a few users feeling neglected, 4.0's improved stability and bonus creativity tools easily make this upgrade worth the price of admission ($149 upgrade).


Like DirectX, VSTi and VST software code is an open standard and thereby infers some creative, innovative and unfortunately incomplete development. Developers of VST effects and Instruments are usually small companies, or even hobbyists, that create with the best of intentions and, unfortunately, the smallest of beta-test budgets. Use caution with all VST Instruments! I recommend that the moment you experience a crash, write down the instruments you have open and then visit both Sonic Foundry's update site at (click on Updates) and the VSTi plug-in developer's site to check for an upgrade. If one isn't available, take the instrument out of Sonic Foundry's VSTi list and write the respective tech-support personnel. A good site for tracking daily version updates is I learn something every day at this site.

In testing a large variety of VST Instruments within Acid Pro, I had only a few minor problems. They usually occurred when I was pummeling my processor with several different instruments or multiple instances of one large one (like Native Instruments B-4) simultaneously. I discovered that once my processing power became an issue, it was easiest to render each virtual instrument to an audio track and then mute or remove the corresponding VSTi or MIDI track. I experienced the best results in terms of stability (very stable) and low MIDI latency (undetectable) when using ASIO. For those running a non-ASIO soundcard, and I realize there are a few, Acid's WDM and MME engine is running better than ever. WDM, in many instances, will even outdo ASIO, depending upon your hardware/software configuration. Note: If you are running an older operating system — such as 98, 98SE or ME — you may experience some minor digital noise, or clicks. Also, running MME will almost certainly cause some major MIDI lag.

I did experience one serious crash while working in Acid. I was working in a new unsaved project, adding and manipulating several instances of one of my favorite soft synths, and boom! Lights out. Lucky for me, 4.0 has added Auto-Save Crash Recovery, which saves the project, as you go, to a temporary file. When a crash happens, you have the option of recovering that session the next time you fire up Acid. I was extra-impressed (and relieved) in this instance when every edit and parameter setting was recovered even though the document had never once been saved (or given a file name).


If you are familiar with arranging in Acid, you surely were elated when 3.0's Paste Insert command became available (Control + Shift + V). The equivalent improvement in 4.0 is the inclusion of alternate time signatures — Acid now allows for any conceivable time signature. You can select among common figures such as 2/4 up to 9/4 or 5/8 to 9/8 from a drop-down menu off the time-signature block. You can also make up your own. I typed in 41/32 just for kicks, and Acid responded without flinching. Of course, you can also insert one or several time-signature changes within a given piece in almost the same method as inserting a project-tempo or key-change marker. One important point to remember is that because Acid is working with audio loops, it is not changing the loop's time signature to coincide with the project, but the other way around.


Automatable effects are among Acid's new feature set, but before you get too excited, let me point out that this automation is performed by using Acid's envelopes (not via MIDI controller) and can only be completed with Acid's own track EQ, resonant filter or flange/wah-wah effects and a growing list of third-party plug-ins (see Fig. 2). This means that like with Acid's pan, volume and bus send envelopes, you still have to rely on trial and error rather than on a MIDI performance. Nevertheless, this is a welcome enhancement for adding moving freq-filter-style life to stale tracks.

According to Sonic Foundry, other third-party automatable DirectX effects (now working in Acid Pro) include the 3.5 release by Waves, the Lexicon PSP 42, Izotope Ozone 2.0, a number of Cakewalk plug-ins, a couple of VST plug-ins from Sonic Timeworks, a freeware resonant filter by Spaztech and VST effects through an adapter such as one from FXpansion or Spin Audio. In the future, expect Sonic Foundry to continue automating its own brand of DirectX plug-ins. In addition, Acid 4.0's bus tracks have been outfitted with controls for volume, panning and effect parameters within your subgroups (via envelopes) or for your entire project.


Within Acid 3.0, MIDI was a little mysterious. For instance, you could have composed 10 albums' worth of material and never realized that Acid had MIDI capabilities. With 4.0's MIDI improvements and the addition of VSTi, Acid is now a viable and professional sequencer. What's more, MIDI is handled in true Acid-like fashion with loops. If you think looping audio is fun, try looping your soft-synth bass lines or pads recorded in MIDI. The memory usage is nil; the response is instantaneous; and just like Acid audio tracks, you can duplicate, detune, cut up, rearrange and otherwise mangle to your liking (using all of the same shortcuts).

Recording MIDI tracks in Acid is easy. Simply press Record, decide what directory the new MIDI information is going to go to, click on the soft synth (or MIDI Thru channel for external hardware), and you're off and running. I will dock Sonic Foundry a couple of points for the obnoxiously oversize Record window, which is the same as the Audio Record window. This window stands tall, front and center, for the duration of the take, thereby inhibiting all fader moves or other mix adjustments that always seem to happen while the track is being cut. (Monitor mix anyone?) On the bright side, once the track is complete, you can take advantage of some spruced-up editing features, such as 4.0's piano-roll editing, step recording, MIDI filtering and master tracks (see Fig. 3).


Sonic Foundry has spent much of 2002 in its optimization lab. The results are at times minor but tend to make Acid more professional and more easily negotiable. For example, Hotkey commands have now been assigned for muting and soloing audio. This feature could be used in live performance or merely for mocking up arrangement ideas. Also, Acid now allows for sequentially previewing multiple loops in the Explorer window, a handy feature for auditioning groups of loops. Other welcome improvements to Acid Pro's interface are the additional envelope-fade types (seen when right-clicking on envelopes). You can now employ Smooth, Sharp and Hold fade-ins and -outs in addition to the Slow and Fast of previous Acid versions. Next up, the overall optimization of the track-panning features in 4.0 allows you to better manage audio signal levels and even includes the option to mix in 5.1 surround sound (see Fig. 4). The most important enhancement is that you can now designate volume to remain the same when panning across channels, whether the sound is mono or stereo.

To make sure I retain my software-snob status, I must dare to demand a few Acid Pro wish-list items for this year's NAMM. First, I would love for the oversize Record window (same window for audio and MIDI) to go away. It could be smaller for starters but must then vanish once tracking begins. Second, it would be incredible for Acid Pro to be able to play loops backward within a given track — not that I'm looking for overtly arty production, but rather a simple effect that comes in handy when making the transition from section to section. Third, Acid Pro might want to afford users the ability to view multiple effects or instruments simultaneously. Although this may open up a can of instability, I often tweak more than one effect at a time.

All in all, Acid 4.0 is a monster release. Whether you are a 3.0 user or a slow-moving Acid 2.0 wizard, 4.0's features are too much to ignore. I will agree that VST effects and ReWire would be healthy 5.0 additions (and my sources tell me that they will be), but more important, Sonic Foundry has stepped up to deliver what power users need the most: a stable, creative workhorse that can remix the pants off of the most unruly of breakout jams.

Product Summary



Pros: More stable. Includes Auto-Save Crash Recovery. Powerful improvements to time stretching and Beatmapper. Enhanced MIDI-editing tools. VST Instrument and ASIO support. Automatable effects and improved interface functionality.

Cons: Huge VSTi screens. No VST effects or ReWire. PC only.

Contact: tel. (800) 577-6642; e-mail; Web

System Requirements

Pentium or Athlon/300; 64 MB RAM; Windows 95/98/2000/ME; CD-ROM drive; DirectX 8.0, Internet Explorer 5.0 (included on installation disc)


Automated DirectX Effects: track EQ, resonance filter and flange/wah/phase

DirectX Effects:
compression, pitch shift, chorus, delay/echo, noise gate, multiband dynamics, graphic dynamics, parametric EQ, paragraphic EQ, graphic EQ, amplitude modulation, flange/wah-wah, smooth/enhance, gapper/snipper, vibrato and distortion