This is answered in the FAQ: You can't do that directly from the app, but you can play your arrangement inside the app and record the audio output with another program set to capture it. A popular option is the Audacity sound editor.
Check out the last question under the "Samples" heading in the FAQ: (link is only visible to registered users) "Audiotool will accept most file formats but it will not take all versions of all formats. Uncompressed files like 16-bit stereo WAVs should work best." Do as
@naswalt
suggested and try with WAV format. Let us know if this solves your problem.
I think you got cut off there, could you include a screenshot of the error you get? Sometimes I record in audacity or protools before I bring it over to audiotool. I always use 16 bit 44.1Hz sample rate .wav files. This seems to be a pretty probe upload friendly method
Do you publish a song and dl it to sing over or do you just record it and upload through probe? I have a terrible sense of key so all the times I've tried recording vocals without a backing track I've completely failed
How can I record and then pass the audio to my computer?]
I just want to record the track of the drum machine