+ (midiChannelMapping ,symbol? "How to map MIDI channels: per
+@code{staff} (default), @code{instrument} or @code{voice}.")
+ (midiBalance ,number? "Stereo balance for the MIDI channel
+associated with the current context. Ranges from@tie{}@w{-1} to@tie{}1,
+where the values@tie{}@w{-1} (@code{#LEFT}),@tie{}0 (@code{#CENTER})
+and@tie{}1 (@code{#RIGHT}) correspond to leftmost emphasis, center
+balance, and rightmost emphasis, respectively.")
+ (midiPanPosition ,number? "Pan position for the MIDI channel
+associated with the current context. Ranges from@tie{}@w{-1} to@tie{}1,
+where the values@tie{}@w{-1} (@code{#LEFT}),@tie{}0 (@code{#CENTER})
+and@tie{}1 (@code{#RIGHT}) correspond to hard left, center, and hard
+right, respectively.")
+ (midiExpression ,number? "Expression control for the MIDI
+channel associated with the current context. Ranges from 0
+to@tie{}1 (0=off,@tie{}1=full effect).")
+ (midiReverbLevel ,number? "Reverb effect level for the MIDI
+channel associated with the current context. Ranges from 0
+to@tie{}1 (0=off,@tie{}1=full effect).")
+ (midiChorusLevel ,number? "Chorus effect level for the MIDI
+channel associated with the current context. Ranges from 0
+to@tie{}1 (0=off,@tie{}1=full effect).")