Once you have your iPad ensemble formed, you may have trouble hearing all the instruments..
You need a mixer to join them all together..

Here are some suggestions for mixers to be used with ipad ensembles to tie into existing sound systems or


ART SPLITMix4 Passive SplitterMixer 4 Stereo Input CH Passive Design Over 90dB of Attenuation

ART SPLITMix4 Passive SplitterMixer 4 Stereo Input CH Passive Design Over 90dB of Attenuation
ART SPLITMix4 Passive SplitterMixer 4 Stereo Input CH Passive Design Over 90dB of Attenuation
ART SPLITMix4 Passive SplitterMixer 4 Stereo Input CH Passive Design Over 90dB of Attenuation
ART SPLITMix4 Passive SplitterMixer 4 Stereo Input CH Passive Design Over 90dB of Attenuation

ART SPLITMix4 Passive SplitterMixer 4 Stereo Input CH Passive Design Over 90dB of Attenuation

http://www.amazon.com/gp/product/B002VX0DCE/ref=ox_sc_act_title_1?ie=UTF8&m=A24JT33HRREUEL

Or
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external image 41u%2BZvspdCL._SL500_AA300_.jpg

http://www.amazon.com/gp/product/B002VX0DCE/ref=ox_sc_act_title_1?ie=UTF8&m=A24JT33HRREUEL

Or for additional channels, something like this may work well

http://www.amazon.com/Behringer-UB1202-Eurorack-Mixer-Inputs/dp/B0002JF5E0/ref=pd_ecc_rvi_cart_4


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You will of course need Cables and adapters to make all this work also!