Region Automation: Portamento Time
One of the many MIDI messages that can be automated. Creating an automation point adds an event with the control change message. Portamento Time is a required feature of the General MIDI GM2 specification.
From the MIDI specification (1996)
Portamento Control (PTC) is a recent addition, and defines a continuous controller that communicates which note number the subsequent note is gliding from. It is intended for special effects in playing back pre-sequenced material, so that legato with portamento may be realized while in Poly mode.
– Portamento Time (cc#5)
Control Change Messages (Data Bytes)
5 00000101 05 Portamento Time 0-127 MSB