Yes, each player (or string) should be sending in its own midi channel, and yes (in your case) the track/channel should be set to "All" (otherwise Logic re-channelizes the incoming note events) so that all your strings get recorded into a single track. BUT -- There's one important step not mentioned here: You have to tell Logic to operate in "Multi-player" midi recording mode, not in "layer" recording mode (see p. 460 in the Logic 9 pdf manual).:
to quote:
Recording Multiple MIDI Tracks Simultaneously
You may occasionally want to record multiple MIDI tracks at the same time. Often this will be data recorded from an external sequencer, or played from a keyboard that is split across multiple MIDI channels.
You can also simply play the same MIDI channel information from your keyboard, but record it to multiple tracks. One reason you would do this is to create layered instrument parts.
There are two operating modes available for simultaneous recording of multiple MIDI tracks: layer recording and multiplayer recording.
• When layer recording: Incoming MIDI events are sent to all record-enabled MIDI tracks. You can listen to all selected instruments before, and during, recording.
• A MIDI region is created on the selected track after recording.
• Aliases of the MIDI region on the selected track are recorded on the other tracks.
The advantage of this approach is that any subsequent edits to the "parent" MIDI region will affect all aliases, ensuring that all layered tracks remain identical.
• When multiplayer recording: Incoming MIDI events are distributed to the various record-enabled tracks, in accordance with transmitted MIDI channel numbers.
• The channel of the incoming event must correspond to the channel of a record-enabled track for this functionality to work.
• If no track with a corresponding channel number is found, the event will be routed, and recorded, onto the selected track.
You should ensure that each of your MIDI controllers transmit on different channels. If this is not possible, simply use different inputs on your MIDI interface and change the MIDI channel of each input, using a transformer object between the Physical Input and Sequencer Input (see "Physical Input Objects" and "Sequencer Input Objects").
To switch from the Layer recording mode (default) to the Multiplayer recording mode
Choose File > Project Settings > Recording, and select the "Auto demix by channel if multitrack recording" option.