The .oma file extension is for a Sony music format file; these files are in Sony's ATRAC3 format and are not supported by Switch unless you have an ATRAC3 driver.
We recently found a source for ATRAC3 drivers and you can learn more on the website at www.nch.com.au/acm/formats.html. Scroll down to 'atrac' under the Proprietary Formats heading.
