Metamorphosis is another one of those Eric Persing projects that you just know is going to get a little weird by the time you're through. It all sounds harmless enough, 21st century beats with a dash of special processing, but this apparently simple idea has grown into a monster three-disc set, with an additional Mac/PC data disc containing Groove Control information. According to the sleeve notes, knocking up grooves of this type is something Eric does to keep himself sane during breaks in more arduous projects, and this particular set is the culmination of four years' such explorations.

Before we start, here's one tip for Groove Control users, at least where Emagic's Logic sequencer is concerned. The Groove Control data that's needed to make the loops run at different tempos is provided in Cubase, Logic and plain old MIDI File format. In days gone by, I always used to copy and paste the files from Logic song documents into my own songs. It's far faster now to open the regular MIDI files folder and physically drag the Groove Control MIDI file onto the track controlling your sampler.

The data CD-ROM includes the new SoundFinder software by QDesign, that allows loops to be auditioned directly from the data CD. Each loop is presented in three ways, for maximum flexibility: in addition to the Groove Control version, there's a regular set of fixed-tempo loops, plus the same loops as WAV files. There are also Groove Menus at the end of each loop volume, where all the loops from that volume are assigned to individual keys in tempo-matched programs. These work by using tuning offsets in the samplers to trim the tempo, so won't work with Emu samplers.

Each disc covers a specific tempo range: 53-93bpm on Disc A, 94-115bpm on Disc B, and 116-164bpm on Disc C. However, the Groove Control versions of the loops can be halved in speed or doubled without sounding too unnatural, so the given tempos are not really a restriction.

The underlying rhythms of Metamorphosis are directed towards the club, hip-hop and rap markets, and none stray too far from the point, which is good news for those working in these genres. However, the processing style on display is up there with previous Persing releases Distorted Reality and Liquid Grooves when it comes to extremeness, so there's far more here than just a collection of gritty, scratchy old funk rhythms with a slight swing. There's distortion, filtering, extreme effects and synthesized sound, the list of gear used in the creation of the samples extends to two pages of hardware and software. This is not a night out with an HR16 and a Quadraverb!

The degree and type of processing varies enormously throughout the library, but at no point are the loops rendered unusable through over-zealous mangling. The loops really groove nicely, while the processing gives them character and depth that would be very hard to find from any other source. FIVE STARS

-Paul White

Sound on Sound magazine Five Star review