Hello,
I want feed the audio in from the Minitaur with my electric bass.
Is there a preset available, which I can switch to the audio in signal?
I don’t understand the manual “You can use the Minitaur to process any audio signal simply by plugging into the AUDIO IN jack. To hear the external audio signal, you will need a MIDI NOTE ON message.” Cause every note from my midi keyboard is a midi note message, or not?
Thanks in advice 
You need to play a not to hear something from the Minitaur.
Okay, I plug in my bass in a preamp, then from the preamp out, I go to the audio in from the Minotaur and nothing comes out…
Please explain, what must I do?
With the midi keyboard everything works fine.
While doing that you need to hold down a note to open the gate. Any note will do.
Also make sure “ext input” is turned up. Try it at 100% to start with.
Is this a good time for this pic?
^ Probably safer than bricks and less messy than tape, 
Also try starting with the envelopes set to 0 attack, 0 decay and full sustain.
Voilà
From the Minitaur v2.2 manual - this should open the gate for external audio, too?
DRONE ON/OFF:
GLIDE + AMP SUSTAIN (Min to Max = ON)
GLIDE + AMP SUSTAIN (Max to Min = OFF)
https://api.moogmusic.com/sites/default/files/2018-06/Minitaurv2.2_Addendum.pdf