Hi John,
How about:
\version "2.19.36"
\language "english"
\new PianoStaff <<
\new Staff = "up"
\relative c'
{ s1 }
\new Staff = "down"
\relative c
{
\clef bass
<< { \stemDown
<
af'-\tweak control-points #'((1.4 . -7) (1.7 . -4) (3 . -2.2) (4 . -2.2))^~
cf-\tweak control-points #'((1.4 . -8) (1.7 . -5) (3 . -3.2) (4 . -3.2))^~
ef-\tweak control-points #'((1.4 . -9) (1.7 . -6) (3 . -4.2) (4 . -4.2))^~
>4
\change Staff ="up"
\once\tupletDown
\tuplet 3/2 { <af cf ef>8 <bf! df! f> <cf! eff! gf!> }
\revert Accidental.stencil
}\\
{
ef,4_~ 2.
}
>>
}
>>Just an example, control points have to be set properly.