History
Yamaha (the company who makes everything) has at certain times made their stab at making a sampler.

The first sampler Yamaha created was the TX16W. It had a lot of potential, being one of the first stereo-sampling units at an affordable price, but other feature-packed samplers surpassed it in popularity.

The next sampler-fling was with the "Prophet 3000" sampler, which Sequential Circuits released shortly before they were going under. Yamaha renamed it the P3000, tried to market it, but very few were sold.

Nevertheless, at the time, Yamaha didn't have the interest to jump into the rapidly advancing sampler game, as FM, digital pianos, among other things, were their niche.

The recent A3000 was Yamaha's jump back into the game. The great thing about it was the massive architecture, with multiple envelopes and processing. The bad part of it was the SCSI interface was about as slow as a floppy. This greatly accelerated the disinterest in the sampler.

The A4000-5000 Series was Yamahas attempt at improving the A3000. The SCSI Interface is still slow, even with being improved slightly, and the unit is difficult to use, using terms and processes different than the mainsteam.

Even so, the great effects and architecture of the Yamaha still have an appeal to those who get familiar with the interface. Some of the interface details are admittingly innovative, such as the comination turn-push knobs, and the multi-button menus.

Architecture Description
Pretty simple - a "sample" contains one sample reference and contains all the keyrange, envelope, LFO, etc. settings. These are put into Programs. You can also organize samples into groups for bulk editing. There are two integrated effects processors, which sound great.

File Format
The A4000 Series use a proprietary format. However, they can read DOS formatted volumes - it just doesn't save to them. The Yamaha proprietary disk format is similar to DOS, but diferent enough to not be read by a computer. They also come with a great 12 CD library, and all of them are readable in DOS format. The Yamaha's can read a number of other formats, including Akai S-1000/3000, Roland S-7x, and Emu E-3 programs/banks.