You are here

Sony Acid Pro 6

Audio & MIDI Loop Sequencer [Windows] By John Walden
Published July 2006

Sony Acid Pro 6

The original loop-sequencing package has grown into a fully-fledged audio and MIDI recording program.

Some may find it hard to believe that the original loop-based music production package, Acid, has now been with us for nearly a decade. Having survived — and indeed prospered — since Sonic Foundry were taken over by Sony's Media Software division, Acid Pro has now reached version 6. When I reviewed version 5 back in the April 2005 issue of SOS three new features really stood out: Groove Mapping, the Media Manager and Rewire client support. The latter in particular was a real leap forward, making Acid much easier to integrate with most MIDI + Audio sequencers. That said, despite better tools for audio and MIDI recording, Acid 5 was still very much a tool for building musical arrangements out of audio loops, so the Rewire support was pretty much essential if more than just the occasional audio or MIDI recording was required within a project.

Of course, version 6 retains all the functionality of previous releases, including an interface that is extremely easy to use, a Video window for working to picture, and automatic, real-time pitch-shifting and tempo-matching of audio loops that is simply as good as it gets. However, Sony have clearly been busy listening to the Acid user base, because the obvious highlights of the new version are the significant improvements to the audio/MIDI recording and editing capabilities. Among a large number of other improvements and additions, Acid Pro now also supports multiple media files on a single track — something that many users have been requesting for a long while. And to top off the new features, Sony obviously have a good working relationship with Native Instruments, as Acid Pro 6 is supplied with a custom version of NI's Kompakt VST Instrument that includes a 2GB sample library.

Keeping You In The Loop

Given that the previous SOS reviews of Acid are all available on-line, there is little point in spending too much time here on the long-established features of the software. Acid 's key function has always been the real-time pitch-shifting and time-stretching of audio loops. These can be manipulated together or independently — making it easy, for example, to alter the tempo of pre-recorded drum loops to match a project, or to pitch-shift a bass loop to fit the project key. Loops can be stored in an ' Acid ised' format which contains information about the original recording tempo, length (in beats) and root-note pitch, and many commercial loop libraries are supplied ready-Acid ised. Like Ableton Live and NI's Intakt in its Time Machine mode, Acid uses granular resynthesis for time-stretching. The results are generally excellent, although as with any pitch-shifting or tempo-stretching, the process only works within certain limits before audio artifacts appear.

The other key component of the Acid experience has always been the user interface. This makes the mixing and matching of loops so simple that, with the right combination of loops, even non-musicians can use it to create very impressive results. The ability to preview Acid ised loops in real time means that auditioning a new loop simply involves clicking on a file as you browse your loop collection in the Explorer window — you will automatically hear it with its tempo and pitch mapped to those of the project.

System Requirements

  • Minimum 1GHz processor with 256MB of RAM: 1.2GHz and 1GB recommended.
  • 150MB hard disk space for program installation, 600MB for optional loops, 2.2GB for installation of Native Instruments Kompakt Sony Acid Pro Edition.
  • DVD-ROM drive.
  • Direct X 9.0c or later, Windows 2000 or XP.

Keeping Track Of Your Loops

Given that it is difficult to imagine how Sony (or the competition for that matter) could improve dramatically upon the quality of the pitch and time-manipulation tools already available, what have they be doing that moves Acid Pro 6 forward? As outlined above, the most significant improvements concern the recording and editing of audio and MIDI, but there are also some significant changes to the user interface, and it probably makes more sense to start with these.

Acid now supports multiple files on a single track.Acid now supports multiple files on a single track.Despite my complimentary comments about how easy Acid is to use, one criticism of the user interface in earlier versions, compared with some competing products, is that each audio loop used within a project required its own track within the Track List. While this did keep things conceptually simple, and despite the very welcome addition of nestable Folder tracks in version 5, navigation around projects that used large numbers of loops (and therefore tracks) could feel a little clumsy at times.

Thankfully, Acid Pro 6 now allows any number of different loops to be placed upon a single audio track. As in any other mainstream audio application, track-level processing such as effects plug-ins is then applied to all the audio clips positioned on that track. To the user, this is a seemingly simple change — although I'm sure it has involved some considerable programming work within the audio engine — but for Acid regulars, it will take some getting used to. Double-clicking a loop within the Explorer window still creates a new audio track within the Track List, ready for that loop to be placed upon, but loops can also be dragged from the Explorer on to existing tracks and positioned alongside other clips. If clips are positioned to overlap, automatic crossfades are created.

Project Sections help both with navigation and rapid edits to arrangements.Project Sections help both with navigation and rapid edits to arrangements.This change brings some obvious benefits. First, it is easier to keep track counts to a manageable size, making project navigation easier. Second, if similar loop types are placed upon a single track (for example, various drum loops or various bass loops), only a single instance of any VST effect is required to process them. This could have been achieved via a buss in previous versions, but the new arrangement is both more flexible and easier to configure.

Another addition that, on the surface, does not appear to be very dramatic is the introduction of Project Sections. In practice, however, this is a significant new feature. With a loop region defined on the Timeline, the Insert / Section menu option (or Shift+S keyboard shortcut) will turn that loop region into a Project Section. These Sections are identified by coloured bars above the Timeline, and users can enter a name for each Section. While this obviously makes navigation through an arrangement easier, the real power is in the ability to move, copy or delete Sections. When a section is moved or copied, all its contents — clips, markers and envelopes included — are moved also. If a clip crosses a Section boundary, it is split at the boundary. If a Section is copied and placed between two existing Sections, then space is automatically made and later Sections are moved further along the Timeline. As simple as the concept seems, it dramatically improves the efficiency with which song structures can be reorganised. It is the kind of feature that you cannot imagine living without, once you've used it.


The most obvious alternative to Acid is probably Ableton Live, which has the advantage of being cross-platform, with a stylish graphical interface, and has equivalents of most Acid features. However, Live doesn't include any equivalent of Kompakt For Acid Pro, and some of its features are implemented rather differently. Other alternatives include Cakewalk's Project 5 and Image Line's FL Studio.

Red Light On

The undoubted highlights of the new features in version 6 are the improvements made in recording audio and MIDI. This was possible in earlier releases, but Acid Pro would not have been most people's first choice for this kind of work. In my own studio, I've combined Cubase SX for audio and MIDI work with Acid for loops for some time, and this was made a lot easier when Rewire client support was added in Acid Pro 5. However, Acid Pro 6 represents a big step forward, to the extent that it is now not just a tool for loops — it can also be seen as a MIDI + Audio sequencer.

Input metering is now integrated into the audio tracks.Input metering is now integrated into the audio tracks.Hardware permitting, Acid now supports multitrack recording of both audio and MIDI. Multiple tracks can be created and armed for recording as required, whereupon clicking on the Record Device Selector button produces a drop-down menu that allows the default hardware input to be changed for each audio track. Input level metering is now integrated into the audio track, and features such as the dB range and peak hold display can be adjusted to taste, making the setting of input levels easy. If you want, you can monitor the signal being recorded through any plug-ins that have been applied to the track. The dry signal is recorded, but the ability to hear the effects is great for vocalists that require reverb in their headphone mix, or if effects are an integral part of the performance. Providing the audio hardware and drivers support low latency settings, this works very well indeed, and is quickly configured from the Record Device Selector drop-down menu.

Cycle mode recording stacks multiple clips onto the same track, and the user can select which clip sits on top of the stack for playback.Cycle mode recording stacks multiple clips onto the same track, and the user can select which clip sits on top of the stack for playback.Cycle recording is now also possible. If a loop region is defined and recording is activated, individual audio or MIDI clips are created for each pass through the loop region. When recording is complete, right-clicking on the topmost clip brings up a drop-down menu from which, amongst other things, other clips can be bought to the front to be auditioned. As with the mainstream MIDI + Audio sequencers, this sort of functionality is great for cycling through a song section until the perfect take has been captured. It is also fairly straightforward to use multiple clips to compile a perfect take from the best bits of each pass. For example, if cycle recording has been used to capture multiple takes of a lead vocal, the Split function can first be used to divide the clips between each sung phrase. The topmost clip for each individual phrase than then be changed until the best comp of the vocal performance is identified.

The major improvement in Acid 's MIDI features is the inclusion of in-line editing. As anyone who has used similar features in something like Cubase SX will know, this makes editing of MIDI data much easier as it can be viewed in context with the timing of events on other tracks. In either the Piano Roll or Drum Grid, note position, velocity (through the use of very intuitive 'velocity stems'), pitch-bend and controller information can all be edited in place. In use, I found this worked very well, offering enough features to make the most common MIDI editing tasks very easy, but without getting bogged down in a glut of features that the majority of users would never need.

Kompakt For Acid

The custom version of NI's Kompakt, with its 2GB sample library, is a nice addition to Acid.The custom version of NI's Kompakt, with its 2GB sample library, is a nice addition to Acid. As part of an ongoing relationship between Sony and Native Instruments, Acid Pro is now shipped with a custom version of NI's Kompakt software sampler. This is not dissimilar to the various Kompakt-based sample libraries that SOS has reviewed over the last year or so (for example, Nostalgia or Vapor) in that it contains a fixed library of sounds that cannot be accessed via another sampler; nor can this version of Kompakt load sounds from other libraries. However, I was able to use this Kompakt VST Instrument within Cubase SX, so while it is a custom version supplied with Acid, it can be used under other hosts.

I suspect some of the samples may be derived from East West's Colossus, and they cover bread-and-butter territory — pianos, keyboards, guitars, basses, drums, synths and ethnic instruments — with well over 100 different instruments in total. Free or not, some of the sounds are very good. There are some very respectable piano sounds and the various synth and bass patches are also good, but my personal favourites were the various drum and percussion programs. Here there is plenty of choice, ranging from acoustic kits through to basic orchestral percussion.

Bits And Bobs

These headline features aside, there are a whole raft of smaller but nevertheless worthy additions and improvements in Acid Pro 6. For example, Acid now includes support for external control surfaces; a generic template is supplied that can be configured for any external controller, and there's native support for Mackie Control and the Frontier Designs Tranzport. Improvements have also been made to the automation, the most important of which is the addition of support for VST Instrument parameter automation. Given the improvements in MIDI recording and editing, this better VST Instrument support will be welcomed by anyone who now wants to use Acid as a complete music production environment.

In-line MIDI editing improves Acid's potential as a useful MIDI sequencer.In-line MIDI editing improves Acid's potential as a useful MIDI sequencer.Options for filtering and processing MIDI data have also been improved, and MIDI File import and export is now supported. In addition, there is now a Drum Map Editor that can be used to create a Drum Map for editing — this is much easier to use than the Piano Roll editor when working with a drum synth or sampler.

I suspect that the audio engine within Acid has undergone significant changes in order to provide support for multiple audio clips on a single track. In use, I certainly did not notice any performance hit because of this — comparison of playback of a range of projects in both Acid Pro 5 and Acid Pro 6 produced similarly smooth results. However, the engine in the new release now also provides support for dual and multi-processor PCs. I didn't get the opportunity to test this (I'm currently building a new dual-core Athlon system, but at the time of writing, it is not yet fully configured) but I'm sure power users will find Sony's explicit statement of support for dual-core systems reassuring.


Drum Maps can be defined for MIDI editing when using drum synths or samplers.Drum Maps can be defined for MIDI editing when using drum synths or samplers.As with version 5, this new release of Acid contains some big new features that make it both revolutionary and evolutionary, and I would think the majority of existing Acid fans would consider the upgrade essential. While I still wouldn't choose Acid over something like Cubase SX if the majority of my work was based predominately around live audio recording or serious amounts of MIDI such as complex orchestral arrangements, Sony have now moved Acid Pro 's functionality firmly towards that of the mainstream MIDI + Audio sequencer, and this ought to broaden its appeal considerably.

The audio and MIDI recording options are now certainly good enough for serious multitrack work and I can easily imagine myself creating complete projects combining loops, audio recordings and MIDI-driven soft synths/samplers entirely within Acid Pro 6. This is not something I would have contemplated in version 5. What's more, Acid remains, for me at least, the only audio software in my studio that manages to both tremendously powerful and also downright fun to use. If you have never taken Acid, there has never been a better time to try it. Highly addictive and highly recommended. 

What Next?

As with any software application, most Acid users probably have a wishlist of additional features that would be useful. My top two would be a more comprehensive mixer window that would allow both track and buss faders to be viewed together, and a function equivalent to SX 's Detect Silence for automatically splitting audio files. The latter would be very useful when doing jobs such as vocal comps in conjunction with Acid 's improved cycle-mode audio recording. It would be even better if there was also a function that could automatically shift all the clips stacked on one track to a series of identical tracks each containing one of the takes. These could then be more easily auditioned, before cutting and pasting the best phrases for each part of the vocal onto a single track to create the 'master' take.

Test Spec

  • Acid Pro 6.0 build 214.
  • PC with 3.2GHz Pentium 4 CPU, 2GB RAM, Echo Mia 24, Egosys Wami Rack 24 and Yamaha SW1000XG sound cards, running Windows XP Pro SP2.
  • Tested with Steinberg Cubase SX 3.1.1.


  • Still as good as it gets for tempo- and pitch-matching of loops.
  • Some excellent improvements to the user interface.
  • Vastly improved support for audio and MIDI recording.


  • If you like to mix and match loops — then not many.
  • Like all Sony's major audio and video applications, it's PC-only.


If your music-making process generally begins with loops, Acid is still as good at it gets, and version 6 can now be considered a very respectable MIDI + Audio sequencer with good VST Instrument support.


£299 including VAT.

SCV London +44 (0)20 8418 1470.

+44 (0)20 8418 0624.