I believe a [DI box][1] can also get your Line Level to Mic Level signal for the iphone to recognize the signal in its mic port. I've not tested this.

 


  [1]: https://www.amazon.com/dp/B000B85FV0/ref=sspa_dk_detail_3?psc=1&pd_rd_i=B000B85FV0&pd_rd_w=ip10W&content-id=amzn1.sym.a53ea610-e450-44d1-897e-68c0c718bf50&pf_rd_p=a53ea610-e450-44d1-897e-68c0c718bf50&pf_rd_r=X6JNEJ8N4853HSNVJSD9&pd_rd_wg=OvUaO&pd_rd_r=c4253f5e-5f91-41c4-8e7e-7a3a92078307&s=musical-instruments&sp_csd=d2lkZ2V0TmFtZT1zcF9kZXRhaWxfdGhlbWF0aWM&smid=A2O1A8NNN5Y1TU&spLa=ZW5jcnlwdGVkUXVhbGlmaWVyPUExMzlHOVNCN01DOU9DJmVuY3J5cHRlZElkPUEwNDIzNjM5MkNWSzNDQzNMUjJUViZlbmNyeXB0ZWRBZElkPUEwMjIyNjcySzhYUTNQTUNJNFRRJndpZGdldE5hbWU9c3BfZGV0YWlsX3RoZW1hdGljJmFjdGlvbj1jbGlja1JlZGlyZWN0JmRvTm90TG9nQ2xpY2s9dHJ1ZQ==