What are you using for your MIDI synth? (I didn't read the whole thread completely)

I hesitate to mention this, because it would seem you must have done this a log time ago, but it could just be that your RealTracks and MIDI synth playpack are out of sync. BIAB has an adjustment for this. Go to Options, Preferences, Audio. You will see settings to delay the audio in milliseconds. You can also run the Soft Synth Latency Adjust (button) and adjust the timing of what plays (both audio and MIDI) until it syncs up.

This adjustment can sometimes need tweaking if your choice of audio driver change, such as from ASIO to WAS.

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Also, I didn't see an answer to AudioTrack's question in which he showed you notation and asked if that was correct. In the first measure, is there a quarter note followed by eight notes, or an eighth followed by sixteenths? BIAB did add the ability to handle some limited cut time signature notation in the last year. It was at the request of Bobflatpicker for Bluegrass, and me for samba.

BIAB 2025 Win Audiophile. Software: Studio One 7 Pro, Swam horns, Acoustica-7, Notion 6, Song Master Pro, Win 11 Home. Hardware: Intel i9, 32 Gb; Roland Integra-7, Presonus 192 & Faderport 8, Royer 121, Adam Sub8 & Neumann 120 monitors.