Talking about gesture and metaphor often gets me into a critical state. I am not sure I agree with McNeill’s idea of opposing iconic and metaphoric gestures (just because they refer to something concrete or abstract respectively). I was also somewhat puzzled by the MPI Lecure on Metonymy in Metaphoric Gestures by Cienki and Mueller. And that was the sort of talking over lunch just now. One of the professors here, Paul Hekkert, is also interested in metaphors. He gave a masterclass at a workshop at the university of Tilburg, as part of their Advanced Studies Initiative on MultiModal Metaphor. We talked a bit about metaphor and gesture, and then… It struck me that in the experience of music people often use the term Musical Gestures, which I think is actually a metaphoric use of the word gesture. As far as I can tell there is no actual gesturing involved, there are just musicians playing their instruments. But somehow, when they play the music in a certain and when the audience picks that up, people start to talk about musical gestures. That would mean that the music played is understood in terms of a gesture. What is a gesture then? Well, let us say now that gesture is the display, through any action, of an intention to communicate. Musical score
A dramatic gesture of “Maternal Love” ? (source)

Going back to the music, we can then say that with a musical ‘gesture’, the musician displays an intention to communicate (his feelings?) through his playing. I guess we should add: ‘beyond that which is displayed through the usual playing of music’. And maybe we should also add: ‘or at least insofar as such an intention is perceived by an audience’. Perhaps it would even be more accurate to add: ‘insofar as an audience chooses to project such intentions to communicate on the performance’. For as far as I can tell nothing is stopping people in the audience from projecting the grandest displays of feelings on the tiniest blowing of a flute. It actually does not matter whether the musical gestures are real (produced and perceived) or imaginary (projected but not actually produced). If I have paid 50 euro to attend a concert I have every right to experience the music in whatever way suits me best.

See also:
The Musical Gestures Project
Journal of Music and Meaning
Meaning in Music Gesture