In seven years of playing the cello I have performed many short works at recitals but never a real concerto with full orchestra. What began as a fun project turned into nine long months of composing, plus considerable effort to typeset the score and 26 parts. Like many composers today, I use an electronic keyboard and MIDI sequencer program to record each part. Once the notes are in the computer, it is simple to change the melody or harmony, or try a passage an octave higher or lower, or maybe move a line from the flutes to the oboes to see which sounds better. It is indeed wonderful to be able to hear a perfect performance of a work in progress without the expense of hiring an orchestra.
Synthesizers are always in tune, and they never miss an entrance.
This ensures that the notes you wrote make it to the score and parts without any errors. The inevitable downside, however, is that a performance by an orchestra of synthesizers sounds decidedly phony. At that moment it became painfully obvious that I would need a real recording with live musicians if I ever hoped to convince a record company or well-known cellist that my concerto has merit. My first thought was to hire a professional orchestra. Then I considered recording one of the local groups I play with.