when i hook up the 3rd keyboard, i just change the p-5 setting to port 3, but no sound
The Track Inspector, with its MIDI Input Port/Channel filter, is very versatile, but that also adds a layer of complexity to multiple controller hookups. I'd suggest that you first go to the Options menu, and disable the
MIDI Override Follows Current Track setting for now. MIDI Override funnels all ports and MIDI input to a single track. Next, make sure that you haven't inadvertently clicked on the Override button (Track Pane; upper-left) while selecting tracks during your setup.
The type of controller, and what it's transmitting, may come into play. Most controllers transmit over MIDI Channel 1 as a default. Some can be changed to other Xmit channels, others can't. An onboard sequencer might use Channel 2, a drum machine, Channel 10, and a guitar controller, 11-16. As a test, set Port 1/Port2/Port3 to 'Omni', but make sure that none of these are set to 'All Ports - Omni'. Project5's default behavior will pick up all controllers and send them to a new track.
In summary, if you want three isolated controllers confined to 3 distinct tracks: no MIDI Override engaged, disable the 'following' Option, and set each subsequent track to 'Port X (
name of controller) - Omni. From there, you can start isolating to MIDI channels, and experiment with controlling multiple tracks, or having multiple controllers triggering a single track.
For more information on external controllers, audio hookups for hardware synths, and sending MIDI out of P5, check out the
Project5 Wiki. A good diagnostic tool can be found
here at TenCrazy.com. Download the MFX PortDiag, install it, and load it as a MIDI FX to each track in question. It'll indicate in plain English exactly what's been funneled into each synth track.