Composing with midi and sampled sounds has become an art in the 21st century. While some purists are opposed to the idea of using samples to represent an orchestra (or any acoustic setting), the current musical climate doesn’t always allow for other options. The opportunities to hear one’s music performed by a top level (or even moderately good) orchestra are frequently reserved for a select few – those who win highly competitive competitions as well as world-renowned composers and artists with personal ties to an orchestral committee. That said, if a composer really loves to write for the orchestra but doesn’t have the opportunity to do so, sample libraries offer a realistic alternative.
In some ways, the lack of outlets for orchestral readings has encouraged and inspired composers to become adept at using midi. Personally, I’ve had great success using Quantum Leap’s East West Symphonic orchestra (Gold) along with various string patches from Omnisphere. However, the sources used are not as important as the ability to manipulate and combine sounds to achieve the feeling of a live orchestra. Sometimes it may be necessary to add a few live instruments to make the recording more realistic…especially since most sample libraries have some deficiencies with certain instruments in the way the sound speaks. Although you may need extra funds to do this, it’s certainly more affordable than hiring an orchestra :)