The Alesis Midiverb II featured a unique reverb algorithm, which Keith Barr labeled “Bloom.” From the Midiverb II manual:

Programs 45 and 49 are extraordinary variations on the reverse reverb theme. They are exclusive Alesis programs that are unobtainable in any affordable signal processors other than MV II. They are named Bloom and have an envelope that rises (blooms) to a rich and highly diffuse reverb with a smooth decay. These are the ultimate for ethereal effects and long, slow introspective musical passages.

The architecture of ValhallaShimmer lends itself nicely towards emulating the Bloom algorithms of the Midiverb II. A screenshot of the settings:

The key to the emulation is to combine Diffusion of 0.5 with a fairly high feedback setting, and use the reverb mode and size control to tune the attack time of the reverb.

  • In the above example, the mediumStereo mode is being used, as it has a fairly lengthy attack with this diffusion setting. This will sound the closest to the original Midiverb II Bloom algorithms.
  • The bigStereo mode can give you super long attacks, as will the mono mode.
  • The smallStereo mode doesn’t have enough density to get this effect – it will sound like a diffuse echo with a Diffusion setting of 0.5.

The Midiverb II Bloom algorithms didn’t use modulated delays, probably due to cost restrictions of the hardware. Adding modulation to the above settings results in a beautiful, washy soundscape, that works well for ambient synthesizer and guitar.

Keith Barr talked about using allpass coefficients of 0.5 in the original Midiverb (due to this being an easy value to get with bit shifts), and that people complained about the reverb taking too long to build. My guess is that Barr created the Bloom algorithms for the Midiverb II in order to take advantage of this “flaw.” Apparently My Bloody Valentine used the Bloom patches a lot – recent photos of Kevin Shields’ rig show two Midiverb IIs in there.