help with melisma and autobeaming

[Russ Ross]

I'm setting vocal music, and I've noticed that beaming seems to follow
normal rules within a melisma.  I normally turn off autobeaming for
vocal lines, but within a long melisma the conventions on old scores
seems to be to follow normal beaming conventions, so I frequently end
up with sections like this:

  a4. g8 a4. b8 |
  g8[\melisma b e d] cis[ d] e4~ |
  e8[ a, d c!] b[ c] d4~ |
  d8[ e16 d] c4~ c8[ d16 c] b4~ |
  b8[ a16 gis] a8[ b] c4. d8 |
  e8[ d]\melismaEnd d4 r2 |

What I'd like to do is set melisma markings to automatically enable
autobeaming for the duration of the melisma.  My naive attempt was
this:

m = { \melisma \autoBeamOn }
mEnd = { \melismaEnd \autoBeamOff }

  a4. g8 a4. b8 |
  g8\m b e d cis d e4~ |
  e8 a, d c! b c d4~ |
  d8 e16 d c4~ c8 d16 c b4~ |
  b8 a16 gis a8 b c4. d8 |
  e8 d\mEnd d4 r2 |

but alas, it failed with "error: syntax error, unexpected
EVENT_IDENTIFIER:" and pointed to \melisma and \melismaEnd in the
definitions of m and mEnd, respectively.

I tried a few variations with no luck.  Even if I get the definitions
right, I'm concerned that the beaming won't start until the second
note, so in the example above I'm afraid the the beam I'd expect on
"g8 b e d" won't include the g.  Would anyone be kind enough to help
me out?

Since this seems like the standard way of doing things at least in
classical music (I'm typesetting Bach) I think it may be worth
considering as a standard part of the distribution.  m and mEnd are
probably not ideal names, but I think the concept is sound.

Anyone else have any thoughts?

Thanks,

Russ