Do large ensembles always need a conductor?
Or, to be clear, do they always need someone beating time? Of course they don't. But, so many music educators who are leading school ensembles make the mistake of beating time, all the time. Let me provide a bit of perspective.
I was recently at a public school concert where an ensemble of terrific young string players were being accompanied by a bluegrass band on 2 fiddle tunes. The conductor of the group, who is a fantastic musician and teacher, was beating 4/4 time throughout the entire performance. It really seemed out of place and even detrimental to the success of the performance. He would have been so much better served to get the pulse out of the way visually, and to give some other meaningful information from the podium. This might include musical cues or appropriate style and/or dynamic information. Instead, he was waving his arms (almost furiously) and not really providing any real visual information that could be used by the young musicians. Ultimately, the pulse driving the ensemble was coming from the professional bass player that was accompanying the group, not from the visual information the conductor was providing. It was a shame that the kids weren't informed of this and encouraged to direct their listening skills in the bass player's direction for the pulse-portion of needed information.
So, when exactly does a conductor discontinue giving pulse and allow the musicians to find that information from a different source? Here are some examples from my experience.
Drum set: Any time a drum set is involved in an orchestral performance, I believe the conductor need not beat time. So many of us string educators are programming eclectic styles repertoire nowadays and a drum set is often part of that instrumentation. In my experience, encouraging the players to use the pulse generated by the drums as their tempo and rhythmic guide tightens up the performance. I look at it this way: if the best rock bands in the world can stay together with a solid drummer, so can my ensemble. The conductor can get out of the way here and give other appropriate cues and style information.
Groove section: If a section of the orchestra is providing a clear groove - perhaps repeated, regular notes, they are essentially providing the information that a conductor would provide with the stick. This can happen in repertoire from Mozart to Beethoven to modern stuff. There is something about repeated eighth or sixteenth notes that can be a great groove for an ensemble to "lock-in" on rhythmically. I refer to this as "the engine" in my conducting work with student groups . I find that if I can get all sections referring to the engine for rhythmic subdivision and tempo information, it makes the performance much tighter.
Pieces that are imitating alt styles that would not normally use a conductor. (ie: bluegrass, jazz, rock) Here, I just find it odd to conduct these styles in the same way I would conduct a more classical piece. Again, if it wouldn't happen in the original concert hall setting, I wouldn't do it in the orchestral setting when we are imitating the other style. At least not continuously.
Music with a heavy back-beat: The idea here is that if a section of the ensemble is providing back-beat, then I would encourage the ensemble to listen to and react to that for tempo and pulse. No, to be clear, I (the conductor) might be working to be sure that the section providing the back-beat is together and steady. But, that probably doesn't involve simply beating time.
Music that is essentially chamber music: This again gets to the idea of being authentic with your performance. If a string ensemble is playing a work that was originally a string quartet or trio, perhaps it doesn't need a conductor beating time throughout the performance. Is this an opportunity for you (the conductor) to pick up and instrument and lead with an instrument in your hands?
Think: Authentic. If the style would not use a conductor in it's original form, it probably doesn't need a conductor in the orchestral form. It also comes down to listening purposefully. Musicians need to know when to look to the conductor for meaningful information as opposed to when to listen for meaningful information from other members of the ensemble . Similarly, they need to know when they are giving them information as well. I sometimes called this knowing when you are the teacher or when you are the student. Everyone plays the role of teacher at some point in a performance. Sometimes it's the conductor. Sometimes it's the first violins. Sometimes it's the celli. Sometimes it's the violas or 2nd violins. It is a very empowering concept.
I took a minute to look up "conductorless orchestra" on the web and really didn't find too much. Here is the Wikipedia entry: https://en.wikipedia.org/wiki/Conductorless_orchestra
Also, here is a great conductorless ensemble: http://afarcry.org/
In the end, it comes down to the condutor providing meaningful information at all times. If the information that you are giving isn't needed, then find something to give that IS needed. Always think about what you are doing and how that visual information is enhancing the ensemble's task and performance.