Today Korg has PA80 and Roland has VA7. Yamaha has Tyros and PSR2100. We even have Technics, Ketron and more. There are newer models on the horizon with new names and numbers. A lot of members here are familiar with the Yamaha PSR2100, which is selling for around $1200. Features vary as prices go up or down. Basically, an arranger provides pre-set rhythms and chordal/bass patterns to accompany a drum machine-style percussion. Things can sound very full and impressive.
This group will tell you all about them, but be prepared to hear subjective cheerleading and bandying about by all sides. Keyboard workstations like the Karma, Triton, Motif, Fantom, etc. are not considered arrangers, but many of us own these boards too to help in our music making.
Well, that's a start - who's next?...