At each band size the question is: would this band be better with more people? How much better? When you go from one to two people the answer is basically always "better by a lot". There are some very good fiddlers that I could have a great time dancing to, but I can't think of a case where pairing them with the right guitar or piano player wouldn't make for a lot more fun dancing. Going from two to three people is also usually a large improvement, but there are some excellent two person bands. Some of them use looping or pre-recorded tracks to fill out their sound while others are entirely live. Still, there's usually a lot a third person can add.

From my perspective the fourth or fifth musician is where you start to hit diminishing returns. There's a cohesion that is much easier at smaller sizes and four or five is where I start to feel it breaking down. Getting even larger, to six or seven, can make sense if you're going for a Ceilidh or Big-Band sound, but with traditional contra instrumentation you often just get people stepping on each other.

With my preferences out of the way, what does booking look like? How large are the bands that get hired to play? I looked over the websites for several dances, and tracked the size of the bands. These are all relatively frequent dances; I looked at the various smaller monthly Boston-area dances but none of them listed the band compositions. I skipped open bands and a small number of bands where I couldn't find the number of musicians anywhere. When a band included the caller (Elixir, Wild Asparagus) I didn't count the caller toward the size of the band. So:

• Scout House Thursday

      2 ***
      3 *********************************
      4 ***********************
      5 *****
      

• BIDA

      2 *********
      3 ************************
      4 ****
      5 *
      

• MIT

      2 ***********
      3 *******************************
      4 ******
      5 *
      6 *
      

• Glen Echo Sunday

      2 ****
      3 ****************
      4 *************
      5 ***
      6
      7 *
      

• Glen Echo Friday

      2 ***
      3 ***************************
      4 ***************
      5 **
      

• Glenside

      2 *****
      3 ***************
      4 *********************
      5 ****
      6
      7 *
      

Some series or dance communities seem to have a preference for trios while others like quartets, and some rarely book duos while others seem comfortable with them. Overall, however, smaller bands are much more common, with no six-piece bands and only a few 7-piece ones.