Digital Audio Workstations (a.k.a. Digital audio sequencers, or just sequencers) form the backbone of most musician’s virtual instrument - oriented set-ups. These programs cover the entire production process from composition to the completed piece of music.
They record audio and MIDI on side-by-side tracks, they host virtual instruments and plug-ins, they’re good at editing audio, they have automated mixing features, they host video clips if you’re scoring, most of them have notation sections…and the major ones have been continually developed over at least a decade, which shows in how sophisticated they are. If you take a step back, every one of the five major DAW’s is an astonishing piece of work.
On the Mac you have MOTU Digital Performer and Apple Logic Audio. Then on both Mac and Windows you have Digidesign Pro Tools and Steinberg Cubase and Nuendo. Cakewalk Sonar is PC only. All but Digital Performer have lighter and heavier versions in their families; all but Pro Tools have notation sections. These programs attempt to be the only program you need, integrating features that used to require a suite of third-party add-ons. They also include a dizzying array of plug-ins and often Virtual instruments.
Yet they all host third-party plug-ins and instruments as well. Furthermore, they’re capable of acting as rewire hosts; rewire is a protocol for streaming other programs and instruments into the DAW’s mixer, with the two programs completely synchronized. You can also trigger a rewire slave with MIDI from the master program, in which case the slave just behaves like a plug-in virtual instrument.
All-in-ones Propellerhead Reason and FL Studio are both self-contained environments that feature a host of (without wanting to set artificial boundaries) mostly electronic-oriented instruments. Reason has its own rudimentary MIDI sequencer, along with an entire virtual rack of instruments and processors. If you prefer not to use the built-in sequencer, Reason can also stream into a DAW via rewire.
Hosts
Some virtual instruments have stand-alone versions, others require a host to run. For a virtual instrument that doesn’t operate stand-alone, then there are stand-alone programs whose main function is to host virtual instruments. Steinberg V-Stack, Plogue Bidule (which does more than just hosting), XLUTOP Chainer, Brainspawn Forte, plasq RAX…there are a lot of them. If you’re going this route, be sure it hosts virtual instruments, not just plug-ins.
Notation In addition to being good for entering, transcribing, and printing music, all the major notation programs are starting to gain sophisticated playback features. For most people, that makes writing in the notation program a whole lot more enjoyable.
Sibelius and Make Music's Finale both have bundled versions of Garritan Personal Orchestra. Garritan is making the same thing happen with his new Jazz Big Band library too. Virtuosoworks' Notion is an integrated orchestra library and notation package. Geniesoft's Overture 4 understands all the major orchestral libraries and has integrated MIDI editing. Overture has been around in various incarnations for years, and it was always a very quick and easy program to use.
The concept is that the markings you put on the score select the appropriate articulation. Stick a dot on top of a note and you'll get staccato, slur it and you'll get legato, put ff before it and it'll shout.
Other notation programs include Sion Software's Quickscore, MIDI Notate's very inexpensive Composer, there's a program called Mozart, another one by Capella software... Notation programs don't get all the attention DAW’s get, and not all of them have sophisticated MIDI playback features or integrated pathways to sample libraries. But it's good to see the connection between notes and music working well in both directions.