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Maybe put a delay between the messages. It's odd that Delay needs the bang GUI rather than just taking the message in an getting the bang from it. Seems to need the bang GUI on the input and the output - probably I am doing it wrong.
[line] only understands lists of up to 2 values. It's a common mistake to assume that [line~] and [line] have the same semantics, but they don't.
The multiple-pairs-in-one-list was a new idea when line~ was introduced with MSP. The behavior was never grafted onto the older Max [line] object.
It is, however, possible to write an abstraction around [line] and some list-processing objects and a delay to do what you want. Examples have been posted to the forum, but you'll have to look around. Offhand, I'd suggest looking at Stefan Tiedje's St.ools or Karlheinz Essl's library.
Grizzle's suggestion may be an alternative, but Max and MSP timing may, in certain situations, not play nice with each other.