I am returning to home recording after a few years off with a new PC. I need a synth for virtual instruments. I will want some warm Mellotronish synth sounds, but also some realistic classical instruments that I would sequence via Midi. When I last was recording, internal synths were still the rage. I assume today all virtual instruments are companies that sell gigabytes of samples which one uses Sonar to sequence, rather than hardware synths? I have a small three octave keyboard I'll use as controller. Would I be researching companies that sell samples with the PC acting as a sampler that changes keys of samples with one's controller? Wouldn't that require all digital samples to be in the same key if I'm going to be playing them on a controller in different keys?

Depends on your genre. Arturia might do a Mellotron emulation and check out Spectrasonic synths.
 
Cakewalk Z3ta+ is a good waveshaping synth.
 

There are plenty of "kinds" of soft synths that use your PC to generate sounds.  Many our Virtual Analogue, software versions of Moog etc. (Zeta as above).   Most are sample-playback synths, that use a prefab library of synth and  acoustic/electric instrument sounds (Rapture and DimPro are Cake's best examples).  There are few "samplers" that let you actually sample a sound internally and work on it.
 
I'm not sure about your question about Keys and chords.  Most shorter keyboards let you increment the actual keyboard by octave up and down the range.  So tho you can't play all 88 piano notes at once, you can play every note, which is an answer to your question, I think.  Kontakt (probably the standard sample-playback synth [tho you can certainly stick your own samples in it] will work with keys/chords, although I think that is only in conjunction with their hardware.  I just got a Maschine Jam hardware controller and you can play the pads like a keyboard and pick only pads that are in your key so it will only play those notes.  "Look ma, no bad notes."  "Well, Johnny, you can't play jazz then."
 
I hope this helps.  If not, refine your question and ask again.  Plenty of people with better answers here.

For home recording you would likely get a virtual instrument. If it's a synth you can program it or buy third party patches if you want more than what comes with it. If it's a sample player it will come with some set of samples, but there are often expansion packs available to expand it from the developer or from third parties. There are different sample formats so you need a format that your sample player supports. HTH. If you have Sonar it comes with some virtual instruments.

DanielVogel
I am returning to home recording after a few years off with a new PC. I need a synth for virtual instruments. I will want some warm Mellotronish synth sounds, but also some realistic classical instruments that I would sequence via Midi. When I last was recording, internal synths were still the rage. I assume today all virtual instruments are companies that sell gigabytes of samples which one uses Sonar to sequence, rather than hardware synths?

There are probably more analogue and digital hardware synths on the market now than at any previous time. And more software synthesisers as well.

They hardware is mostly much more affordable than it used to be a couple fo decades ago as well. What has pretty much disappeared is hardware "General MIDI" specification sound modules and keyboards which simply had astandard set of "instruments" such as "piano", "bass", "oboe" etc. of usually pretty unrealistic quality, and intended to ensure that MIDI files for the music in e.g. games sounded roughly the same no matter the platform they were played on. Nowadays software-based samplers do a much better job of impersonating the "real thing".

DanielVogel
I have a small three octave keyboard I'll use as controller. Would I be researching companies that sell samples with the PC acting as a sampler that changes keys of samples with one's controller? Wouldn't that require all digital samples to be in the same key if I'm going to be playing them on a controller in different keys?

Samples of instruments that are intended to play as an instrument rather than audio loops generally load into a software sampler instrument. Rapture, Rapture Pro and Dimension Pro are the Cakewalk ones, there are many others from e.g. Native Instruments and IK Multimedia to name but two. The sample instruments supplied by the sampler manufacturers generally need no user intervention to ge them into the right key or pitch, the software instrument takes care of that. Providers of sample libraries usually either supply a suitable player for their product or state which sampler(s) their product works with.

Pre-recorded audio loops (short passages of up to a few bars, some people build entire compositions based round them) may need re-pitching to get into the desired key, but pretty much every DAW can handle doing that. Though if taken too far from original pitch loops can start to sound a bit strange.

In short, don't over-think this. Most of the hard work has already been done by hardware and software instrument designers and sample creators.

Kontakt, by Native Instruments, and Play, by EastWest, are pretty much top of the line sample-players.
 
There are incredible libraries available for both, both commercial and free.
 
I happen to have need for many of the Mellotron sounds, and there are several instruments/libraries for Kontakt that sound incredibly good.
 
You may well, alternatively, be able to get pretty close with sounds, with Dimension Pro or Rapture Pro (Cakewalk).
 
Bob Bone

For Mellotron consider G-Media M-Tron (Pro).

Thanks all. Lots of great ideas to consider. It took me a few minutes to recognize that your references to sample players, like Kontact, would all be software, which appealed to me as I'll be using a PC for recording purposes only. I assume the programs you mentioned would be opened separately from Sonar, but I'd be pulling them up as instruments WITHIN Sonar? Should I use my old Sonar 2 or to manage these new samplers would it be better to buy a latest version (I noticed there were cheaper version like Home Studio or Professional (which are cheaper than Cakewalk or Sonar versions used to be in the 2000s!). I'll be recording some keyboards, all guitars, and voices via mixer outputs one track at a time, but for the samplers you mentioned, will the new Sonar versions like Home Studio or Professional have easy midi editing of my sampled keyboard parts, like Sonar 2 had? Finally, any easy way to build percussion, a drum machine program that works with Sonar but won't need me reading 300 page manuals! I want to focus on musical creating!!!

If you are buying already, I think the top version of Sonar (Platinum) still comes with Addictive Drums 2 which is a great drum program for acoustic/real drums - it comes with three kits and lots of midi loops and you can obviously edit the loops in Sonar.

The programs we're talking about will occasionally work as stand-alone but mostly you'd open them within Sonar, they're called plugins or virtual instruments or sometimes VSTi (Virtual Studio Technology instruments, a standard devised by Steinberg).

Kontakt is pretty much the standard for software samplers these days. You can buy it separately or as part of a bundle called Komplete which comes with a bunch of other sound expansions and other software synthesizers and fx. Currently the manufacturer, called Native Instruments, is holding a sale I think.

Altogether you'd be looking at quite a lot of money, around 600 for the top Sonar version and another time something like that for Komplete, even with the sale. M Tron Pro is cheaper but it also depends on how many expansions you want with it. With Sonar comes a basic version of Melodyne which is an awesome vocal editor (can also be used for other stuff) that you may want to upgrade for another 200 euros or so. It's really easy to spend your money these days :)

But still a lot cheaper than buying a Motif or Triton ten/fifteen years ago. And obviously you can go step by step, you could get a simpler version of Sonar, or you could get the top version but wait with buying Komplete or Kontakt (because it already comes with loads of stuff).

Welcome back to the world of recording, Daniel. I was where you are about 14 years ago, returning to it after a long hiatus. At the time I didn't know what was out there, but was very pleasantly surprised when I found out! I landed on SONAR because I had used the Cakewalk MIDI sequencer back in the 80's. That turned out to be a fortuitous accident.
 
If you were running a somewhat more recent version of SONAR, say version 5 or later, I'd recommend staying there for awhile until you'd had a chance to build up a Kontakt library collection. But given that you're at version 2, that's not possible. That version simply won't do the job anymore in today's environment because it lacked VST support.
 
So your first priority, before you start buying samplers and sample libraries and soft synths, should be to upgrade to the current version of SONAR. Ideally, that would be the Platinum edition, which comes bundled with a lot of good instruments and effects. So do the less-expensive versions, but Platinum has them all, including Dimension Pro, Rapture, Z3ta and Addictive Drums. Plenty to keep you out of trouble for a long time.