Although I have been performing with orchestras for a number of years, conducting an orchestra rehearsal is definitely not as easy as it looks. A music teacher who has studied orchestral music for years before stepping up on the podium are much better off. These teachers are usually well accomplished musicians themselves who have at least a general knowledge of all the instruments and how to play them.
I believe the first step in conducting a rehearsal for orchestra, whether you are an advanced orchestral performer or not, is to read music. A good orchestra teacher/conductor needs to know how to read various types of music. All of the orchestral instruments don’t play in the same key or even the same clef. Percussion music looks different from the music written for stringed instruments.
Along with reading different types of music, the primary responsibility of the orchestral teacher/conductor is to keep the beat and have good rhythm. Unless you are conducting a professional group, the orchestra will never be able to stay together. Depending on the music, professional ensembles, on occasion would have issues staying together without the beat-keeping of the conductor. Without a common beat, a group of musicians would never play music together. To keep the beat, the orchestral teacher/conductor must have a good sense of time, and know how to read, interpret and conduct all the time signatures, and know how to define musical phrases like andante, adagio, allegro, etc. Without a good awareness of the time signature, the teacher/conductor will not be able to signal the down beat, or major beat of each phrase.
There are many instrument sections in the orchestra, and the music teacher/conductor must be able to locate them correctly during a performance to properly cue soloists and solo sections. An orchestra conductor must signal a certain section when to begin playing after a long rest so that they all begin at once. In order to cue a section correctly, the...