Arrangers are generally keyboards with built in sequencing capability, they allow you to record synth parts and put together actual compositions. However, if you are using a DAW program like PT, Sonar, Cubase, Reaper or any of the other production platforms that support midi, you don't need a keyboard that has this capability. You'd be paying money for a feature you'd never use, and truthfully, it's much easier to compose, arrange and edit midi based pieces in an actual DAW platform than it is on board a keyboard "arranger".

Synthesizers are keyboards with built in sounds - or 'patches" - some let you sculpt and create other patches around the originals that come with the synth, and you can store these creations to either internal memory or a disk drive of some kind. Several also offer extended patches and sample libraries via cards/discs.

Controllers are generally meant for triggering other sounds that exist externally (vst's, other synth modules, etc) and while some come with some basic patches, that's not really what they are designed for.

There are several things you need to consider - if you are using this for live as well as recording, then you'll probably want an actual synth as opposed to just a controller... you could use a controller if you were also looking at carrying around a laptop that had VST libraries, or an externbal tone module that held a variety of sounds/samples, but if you want to just set it up and go in a live scenario, then you'll want something with a good selection of patches ITB (in the box), that also have good sounding patches.

For studio use, you don't need to worry about internal sounds, really, at all, if you are midi'ing up to a DAW program that also hosts VST libraries. In that situation, it would really come down to the feel of the keyboard (synth action, weighted action, hammer action, etc) and how full of a scale keyboard you'd prefer. You can get controllers with as few as 12 keys or as many as a full scale 88 with hammer action that comes very close to the feeling of a real piano's action. I don't rely on Casio for sounds, but I use an 88 key hammer action controller made by Casio that's great. I don't care about the sounds because I use all VST's. As a side note you would also need a midi interface for your computer. You can get them in standalone USB form, or, many USB audio I/O devices also have midi I/O as well.

If most of your work would be piano based, then I would suggest hammer action in 76 to 88 key scale. That being said, hammer action keyboards aren't the easiest to play if you are going to do faster synth runs, B3 sweeps, etc., because those things are much easier to play on faster action boards...either a synth action (fast) or a semi weighted action (medium fast) feel. Weighted and Hammer actions will suite piano productions better than they do synths and organs, because they feel very similar to a piano.

If you gave us a little more detail as to what you want to do, the type of music you are into, the type of music you'd be playing live, and your experience level on keyboards/piano as well as your experience level with digital audio and midi production, we might be able to help you further.

-d.

Thanks for the detailed explanation! A little detail from my end: I am part of a band where we record vocals, and then add in guitar and some instrumental pieces. I have been using a friend's basic Casio keyboard (with unrealistic sounds) to play my instrumental pieces. However, since I use a DAW and MIDI, and I have a good collection of VST instruments, it doesn't really matter what keyboard I have for recording purposes. However, for practice sessions, it would be nice to have a keyboard with rich sounds and features. I don't play live very often, but if I have a decent keyboard, I might do it more. So that's basically my situation. Willing to spend about $500, but if something really nice is a little north of $500, I would consider it.

Bottom line is that, I'm not really a keyboard pro, so I don't need a $2000 keyboard with a ton of features. "Prosumer" quality is what I'm after.

What kind of sounds are you looking to get from this keyboard? Do you want a few octaves? Do you want realistic organ/piano/string sounds or more analog modulation... With out knowing this, I'd have to say a used Roland V-Synth is a good all-around contender.