Bitheadz Unity Session

Sampling and Synthesis Software

Reviewed by Carlos Garza
Originaly Published in Pro Audio Review.

Have you ever thought that the difference between sampling and synthesis is obvious? I used to think so, but that line has been getting blurry for years. Unity Session from Bitheadz is a sample and software synthesis editing environment that provides a single interface for its multiple sound generation engines. Unity closes the gap even more by combining multiple architectures in single instruments.


Unity Session combines the DS-1 sampler, AS-1 synthesis, physical modeling synthesis, and a plug-in architecture that includes MIDI and audio effects. It is only available for the Mac OS. DS-1 was previously reviewed in Pro Audio Review (see the _____ issue). The modular approach described in that review is also present in Session. Separate applications provide editing, live playback, mixing, and MIDI input selection. On screen keyboards provide click and play sound previews.

We reviewed version 3.0.6, which recommends a G4 with 256+ MB RAM, Mac OS 8.6 or higher and 2 gigabytes of disk space for the complete installation. Bitheadz claims to have rewritten the core code base to take advantage of OS X, the AltiVec, and multiprocessors. We tested the package under OS 9 and OS X on a G4 dual 1 GHz Mac with 512 MB RAM. For sequencing, we ran the RTAS plug-in in Pro Tools 5.3.1.

Unity ships with a companion sample ingest application called Osmosis. While Unity can read Gigasampler format natively, other formats, such as AKAI and Roland can only be imported into the Unity environment using Osmosis.

Unity provides a synthesis engine that is compatible with AS-1 patches. It features up to three stereo oscillators and two stereo filters per voice. Also included are synthesis plug-ins for physical modeling of bowed strings, flutes, clarinets, and hammered strings. Programs based on sampler, physical modeling, and synthesis plug-ins can be combined into layered or split instruments.

In Use

Getting the most out of Session requires patient attention to configuration parameters (as we found with DS-1). Getting the memory, sample buffer, processor use, and other parameters at their optimum settings requires trial and error and, oh yes, it helps to read the manual. An email exchange and a phone call with Bitheadz tech support was all I needed to get things working properly. I’m happy to report that Bitheadz tech support was prompt and knowledgeable.

The only snag I found with installation process is the attempted placement of the entire 2 GB sample library in my System Folder! This is clearly not workable if you have repartitioned your drive a created a smaller boot volume. I’m told that this will be fixed in an upcoming release.

I focused mainly on the editor and mixer components for my testing. I found that some operations are a bit slow under OS 9. I also experienced a few crashes but these may have been due to extension conflicts or incorrect settings. I also tested the mixer under OS X and was pleased to see that the application loaded much faster, the screen redraws were faster, and the application is much more stable.

I also tested the Osmosis sample import application. Osmosis had no trouble with the Miroslav Vitous Mini set  (AKAI) or the Ultimate Strings library (Roland). Both were on CD. The program was also able to read my zip discs with a few other sample sets that I use in my live performances. Osmosis creates an editor document for each volume that is ingested. The editor document contains the samples and sample zone layouts for each program. Samples can also be ingested indecently from their programs if you want to use them directly in an audio application.

Even though a variety of sample formats can be read Unity Session does not necessarily support all parameters native to each format. Whereas the AKAI format supports individual volume and filter envelops for each sample in a program, the DS-1 architecture provides envelopes only at the program level. Be aware that your sample library may not behave exactly as it does in your native sampler.

I was amazed at the sound of my AKAI library through the 96 I/O converters on my Pro Tools HD system. Granted, the comparison is unfair given the age difference between my S2000 samplers and the HD system and their intended use. However, the point is that making use of my existing sound library without having put them through analog and back to digital is a big plus.


The samples provided are a good starting point for any collection. I’d like to see more attention in the General MIDI set since these tend to be the most useful sounds. The pianos are workable but if you are serious, you may want to look into a higher end orchestral set. Speaking of which, the ability to ingest popular sample formats such as AKAI, Roland and Gigasampler mean that a good supply of high-end samples is readily available.

At version 3.0.6, I saw very few crashes. Still, I’d like to see some improvement in the stability of the product and speed in loading sounds under OS 9.

If sample playback alone is what you are after then you may want to look at DS-1. If you are interested in a product that mixes samples with a variety of synthesis architectures then Unity Session might be for you. It packs a lot of punch into a versatile set of tools.

At a Glance

Applications: Software sound module for sequencing and live performance

Key Features: synthesis, physical modeling and sample editing; imports AKAI S-1000, S3000, Roland S-760, S770, and TASCAM Gigasampler formats. Also reads Bitheadz Retro AS-1, and Unity DS-1 sound sets. Supports Logic, Pro Tools, Digital Performer, Cubase and others.  OS X support.

Price $649

Contact: Bitheadz: 888-870-0070

Product Points


  • Single interface
  • Pro Tools HD compatible
  • 96k sampling rate
  • Reads AKAI, Roland, and Gigasampler formats
  • Ability to combine synth programs, physical models, and samples in a single Session “instrument”


  • Mac only
  • Configuration intensive
  • Could be more robust

The Score

A good value considering the multiple synthesis engines, the ability to ingest AKAI, Roland and Giga sample sets, and the helpful support staff.

(c) 2003 Carlos Garza