Product Reviews

Traditionally, the PC music-creation tool has been the sequencer. It built compositions in terms of sequences of data, covering what notes to play on which instruments, when and for how long, sent via MIDI to a synthesiser engine, which interpreted the data and output the appropriate music to its audio-outs. As the sequencer improved, it gained the ability to trigger the playback of pre-recorded digital audio snippets stored on a local hard drive. In this way, recordings of conventional instruments could be stored and played back alongside synthesised music.

For many modern musicians, however, working with digital audio snippets has become the most important part of the process. Most popular music is based around repetitive rhythmic and melodic motifs, which, once recorded, can be looped and inserted in the track when required. It isn't that simple, however. Once recorded, digital audio loops are of a fixed tempo and pitch. If, during the composition of the track in the sequencer, you want to change the pitch and/or tempo, the loop either has to be re-recorded or the tempo or pitch must be shifted in a wave-editing package. It's a fiddly and frustrating process.

Sonic Foundry's Acid solved these issues at a single stroke. It plays back any number of WAV files simultaneously, depending on your system, either looped or once. Editing is as simple as dragging WAV files from the Explorer window onto the Acid grid, then using the Pencil tool to size the clip over the appropriate number of 'bars'. Each WAV file deposited on the grid occupies its own track, with the horizontal axis representing time.

Where Acid really works is in its behind-the-scenes processing. WAV files that have been Acidised have the tempo and pitch stored alongside the rest of the wave data. If you set the master key of your composition to A and the tempo to 134bpm (beats per minute), then drop an Acidised WAV file of 120bpm in the key of C onto the grid, Acid will automatically pitch and time-shift the WAV file in real-time to run at 134bpm in the key of A. With files that haven't been Acidised, the program estimates the raw bpm of the file and uses this instead, with a surprising degree of accuracy, even if it ignores the pitch. If you know the key of a file you've imported, you can Acidise it yourself by editing the properties

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sheet for the file and entering the pitch. Acid will shift it automatically. Pitch shifting can also be performed manually.

While your composition is playing, clicking on a WAV file in the explorer window prompts Acid to preview it looped in time alongside your song. In this way, browsing through riffs trying to find patterns that match is a swift and simple process. You can even superimpose volume and pan envelopes over tracks, allowing custom fades and pan sweeps to be set up.

The completed composition can be saved as a single stereo WAV file ready for burning onto CD, or in NetShow Active Streaming Format for use on Web sites. There's also a facility to record tracks using your sound card's audio inputs, provided it supports full-duplex operation.

While Acid Music doesn't feature all the functionality of Acid Pro (support for DirectX plug-ins and 24-bit audio support, for example), in most other respects it's identical. It offers a selection of loops in the Rock and Dance categories, with over 620 WAV files included, and it can be upgraded with Sonic Foundry ExpressFX DirectX plug-ins but can't be synchronised with other music programs. On a smaller budget, limited versions known as Acid Style have become available, featuring specialised sample libraries for one genre of music. So far Rock and DJ versions have been released.

Acid Music is a superb compositional tool: even if you aren't a fan of working with loops, it's a useful way of throwing ideas together quickly prior to proper recording using sequencers.

There are drawbacks, however. The pitch and tempo shifting algorithms are excellent, considering they're performed in real-time, but there's an inevitable loss of quality, especially when changing either radically. For the best results, loops should be re-recorded in the appropriate tempo and pitch prior to mastering. There are also a couple of features absent, including a software tuning fork to aid identification of root notes of loops you've imported and, more importantly, a fully-featured wave-editing package. You can specify an external editor to use with Acid Music, and Sonic Foundry's own Sound Forge 4.5 is ideal with its facilities for working with Acidised files. However, a limited integrated version would be a useful inclusion, and would also improve Acid's ability to handle more complex looping. Although you can specify a sample to begin playback partway through, it's a fiddly business getting everything synchronised. Also, many one-shot WAV files have sections that would be ideal for looping internally, and there's no facility to handle this.

Sonic Foundry has obviously acknowledged the arrival of cheaper rivals like Mixman. If you intend using the package primarily for musical doodling, Acid Music is excellent value. On the other hand, if you want to master DirectX plug-ins and 24-bit operation, Acid Pro would make a better purchase.