Memos synced from your computer appear in the Voice Memos app on iPhone, but not in the Music app. Voice memos synced from iPhone to your computer appear in the Music list and in the Voice Memos playlist in iTunes. Select Music at the top of the screen (between Apps and Movies), select Sync Music, select “Include voice memos,” and click Apply.

Sync voice memos with iTunes: Connect iPhone to your computer, then in iTunes select iPhone. If you delete a synced memo on iPhone, it's copied back to iPhone the next time you sync with iTunes, but you can’t sync that copy back to iTunes a second time. Once the device is connected, iTunes may prompt you to sync your device - click 'No' or 'Cancel. Then, go ahead and connect your iPhone, iPad or iPod with its USB cable to your computer. It also supports iPhone X, iPhone 8/8 Plus, iPhone 7/7 Plus, iPhone 6/6s and other previous models. You can export voice memos from iPhone to computer in bulk or selectively.

When you delete a synced memo from iTunes, it stays on the device where it was recorded, but is deleted from any other iPhone or iPod touch you synced. To transfer voice memos to your computer from your iPhone, iPod or iPad, first open iExplorer on your Mac or PC. It is two ways transfer: iOS devices to computer and vice-versa. Memos on your computer or sync them with another iPhone or iPod touch. You can sync voice memos with the primary iTunes library on your computer, then listen to I found some information on page 106 of the iPhone user guide that might help:

Transfer iphone voice memo to mac