I’m using the Audio Damage Odio for that. It brings up the volume to Eurorack level so audio could be passed through and send back for effects, could be recorded and/or the iOS synths could be used to be processed by the external gear. If I want to sync it to tempo I have several options for that, most logical would be the MPC as masterclock through midi and/or CV/Gate by creating a separate track to send a pulse.
Having looked at several VCA’s I’m in doubt.....yes I definitely see some advantages on expanding with such a module, but my current setup already has quite a lot of attenuation possibilities. So an extra VCA could be added later on, it’s not necessary at this specific moment. Rings seems to be fun although I question myself if I’m going to use it actively....also got a resonator app within miRack and another separate plugin. Although I expect the physical Rings module would sound better, the characteristic is already there. Peaks seems to be fun for its diverse functions, envelope, lfo, small sequencer etc. Have also been thinking of an extra oscillator but also think I got that covered too.
Moog Grandmother (2 oscillators, a 3th when using the LFO)
Moog DFAM (2 oscillators)
Mutable Instruments Braids (1 more exotic oscillator)
Mutable Instruments Tides (1 “limited” wavetable oscillator)
iPad with a lot of sources for sound.