Just sharing what I have learned. I have a 64gb usb with about 12,000 songs on it. This did not work in the QX60. Yes it would play but I could not use voice commands and it only could bee about 1/2 the files. I dropped to a 32gb usb and was able to put about 7500 files on it. Works like a champ. I think the QX60 has more of an issue with the 64gb drive than the true number of files.