Following up to this thread :

https://www.ehx.com/forums/viewthread/8314/

The use of a mini mixer, although is the most flexible approach, where you can activate just one unit or any combination of 2,3 up to 4 (limited by the mini mixer channel) – in practical, it’s not quite usable as there seems to be a ‘pop’ sound caused by the mini mixer return every time a new patch (loop switch) is pressed. To use this configuration, you need to mute the loop switcher before changing patch.

A simpler more effective way would be to bypass the mini mixer and route each 9’s wet output to the switcher returns. However you can only activate one ‘9’ at one time. The use of the Loop 1 Silencer is optional, but this helps the usability of Synth 9.

4 patches were created, each activates one of the ‘9’. All pedals are turned ON all the time. This setup enables a few more future ‘9’ to be added