It would be hard to find a better example than this video of a leader carefully setting the right tempo, driving the band along, directing the musical traffic and making very clear what is wanted from everyone, while working up some great excitement in the music.
The leader is the cornet player Shaye Cohn and the tune is Fats Waller's Minor Drag. Click on the link below and hold on to your hats. Note all the subtle signals Shaye gives by means of eye contact, body language, quick words to John Doyle (clarinet) and Barnabus (trombone), a hand signal to Robin (washboard), the notes she holds at the ends of choruses - even left hand on the head to signal a return to Theme A!
Click here to watch.
In other videos, you can even see Shaye 'conducting' the band by extending a bare foot! She does so near the end to indicate that this is to be the final chorus. For example: CLICK HERE. And for another example of Shaye showing great energy, drive and imagination, both in her own playing and in the direction of the band, look at this wonderful performance of Weary Blues: CLICK HERE.