External MIDI instrument audio shows up but can't monitor instrument sound

[alfredo]

I'm thinking I'm doing something very basic wrong. My synth's audio is going into Input 1 on my Scarlett 4i4. Set up an External MIDI track in Logic Pro X and the 4i4 is registering that there's audio coming in, as is the MIDI track and an additional audio track (set to Input 1).

I'm monitoring through the iMac with headphones ('Sound' set to 'Built In Output' in Logic and iMac) and I can hear everything on the track except the synth. I can record the synth as an audio track and it plays back fine. I can also hear it while it's recording.

Scarlett is also patched into a separate amp and monitors, and I can hear everything listening that way. Any ideas why I can't hear the synth in real time through the iMac headphones input?

Only taken me 2-3 hours of fault finding and googling, hence the late post!

[MarkOne]

Have you checked the ‘I’ input monitor button on the channel?

[James Perrett]

A MIDI track normally needs to be sent to a synth if you want to hear anything. Do you have it sent to a synth of some kind? If you are sending it back to your external synth then do you have local off enabled on your synth so that you don't get a MIDI feedback loop?

[muzines]

If you are using an external MIDI track, then you are not sending the sound of the synth into, and through Logic. In this case, you need to route the synth's audio from the inputs in the *interface* to the interface outputs - you do this in the Focusrite Control Panel app.

If you do want to send the audio from the synth into Logic, using the "External Instrument" plugin on a software instrument track, which handles both MIDI and audio to and from the synth, and brings the synth's audio into Logic's mixer. This is a more convenient way of having a separate MIDI track, and and audio track in input monitor mode to handle the audio.

For anything except the first case, you'll need to make sure "Software Monitoring" is ticked in Logic' audio preferences.