Lest anyone be frightened away from using negative p3 values, I just
wanted to point out that the statement quoted below is not quite
correct.  Or that at least it's open to some interpretation.  In fact,
it is possible to have multiple instances (usually, but not necessarily,
notes of different pitches) of the same instrument held simultaneously
via negative p3 values.  This is accomplished by adding a decimal part
to the instrument number.  E.g., to hold three copies of instrument 10
in a simple chord:

i10.1    0    -1    7.00
i10.2    0    -1    7.04
i10.3    0    -1    7.07

Subsequent i-statements can refer to the same sounding note instances,
and if the instrument definition is done properly, the new p-fields can
be used to alter the character of the notes in progress.  For example,
to bend the previous chord up an octave and release it:

i10.1    1    1    8.00
i10.2    1    1    8.04
i10.3    1    1    8.07

The instrument definition has to take this into account, however,
especially if clicks are to be avoided.  To be fair, it's likely that
Richard Dobson knows all this and just meant that the decimal instrument
number notation couldn't be used in conjunction with real-time MIDI
(which was the context of the discussion), in which case the instrument
would be monophonic while a note was held, as he states.  (At least, I
think that's right.)

David Kirsh

Richard Dobson wrote:
> 
> A negative p3 does not only make the note hold indefinitely, it makes it
> monophonic - ...