instrument track only plays one track at a time

All MIDI tracks still produce sound

I think you're talking about what happens in the normal situation, when an instrument is loaded.

Just to take this a step further, I think it's interesting to notice what happens when no instrument is loaded. Let's say you put a region containing midi on a midi track which has no instrument loaded. Since there is no instrument, we can assume that no sound is being produced, but the track meter lights up anyway. So I think the meter in the track header is not really an indication of sound, but an indication that Logic is reading midi on that track.

The track meter on that track will go dark if the region is muted, and/or if the notes inside the region are muted. But the meter will not go dark if the track is muted. This also seems to indicate that the meter is a reflection of midi being read from the track, before that midi is even delivered to an instrument (which may or may not be present).

still plays only one instrument track at a time

I think this project might be damaged, and it would be great if we could take a look at it, as Bee Jay suggested. In the meantime, you should try what Erik suggested about option-click. And here are a few other ideas, although I'm not too optimistic.

Select any region and press S. Three things should happen: this region should have a yellow outline, the ruler should turn yellow, and the solo button in the transport bar should turn yellow. Press S again, and those three things should revert to normal. Is this what happens? It just might be helpful to know.

In the Mixer window, find the button at the top that says "All," and select it. Make sure to look at every channel strip. No yellow S button anywhere? Do you see any Mute buttons flashing?

Press option-K to open the key commands window. In the search box, type "solo off" (without the quote marks). You will see the command 'Solo off for all.' Probably no key is assigned. Give it a key (option-1 might be a good choice, because it's probably available). Close the key commands window, and press the key stroke. Better now?

The channel strip meter still shows that the instrument is playing but there is no sound. When I click back on that channel strip I can hear the sound again. Although the channel strip meter works, the strip in the mixer doesn't show any signal at all.

I have a feeling that when you say "channel strip meter" you mean 'track header meter.' Because it's completely normal that when a midi track is muted (e.g., because another track is soloed) that the track header meter will keep lighting up, even though there's no sound and even though the meter in the mixer (on what is properly called the channel strip) is dark.

The meter in the track header is just indicating that Logic is reading midi from the track. Whether or not that midi gets to become sound is something that happens downstream, and is not reflected in this meter.

45rpm wrote:
I have a feeling that when you say "channel strip meter" you mean 'track header meter.' Because it's completely normal that when a midi track is muted (e.g., because another track is soloed) that the track header meter will keep lighting up, even though there's no sound and even though the meter in the mixer (on what is properly called the channel strip) is dark.

That is right. All MIDI tracks *still produce sound,* when muted in fast ("numpty") mode, so that unsoloing or unmuting has immediate effect. The tracks header meters demonstrate this. The sound is actually stopped in the mixer, which is why the corresponding meters in the mixer don't show activity.

hey there,
i just recently had the same problem and trust me it is the solo track option.
now i know what your thinking cause i thought the same thing, "i checked each track, SOLO IS NOT ON ANY OF THEM!" don't worry, aside from the option to solo each track individually, there is an option to solo all tracks depending on which one you highlight. that is what happened to you (and me).
to fix this do the following steps.

1. open up that particular file you are having this trouble with.
2. go to the "window" option up on the menu screen.
3. scroll down and select "transport" from the window screen.
4. i long transport bar will show up
(you'll know because it has play,record,rewind and all that stuff on the left, and some odd buttons on the right)
5. there should be a yellow button on the right hand side of the transport screen (this is the universal solo button) click it to turn it off).
DONE 🙂
odds are we both hit some sort of shortcut/hot key to turn it on accidently and didn't realize it (lord knows theres a thousand hot keys on logic lol)
hope this helps.

Can you upload the song file somewhere? Strip out all the non essential stuff, and don't include any audio, just the song file, and upload it, and we can take a look at it.

Or, in stead of the yellow button, just hit the S key.

Try option-clicking any solo button in the mixer, twice.