The task consists in recording and writing the Audio directly into the HDD... Will I have bandwidth problem with a normal Hub
I'm assuming this will be a HS-USB 2.0 hub. If so, you have 15MBits/s bandwidth on the USB port that will be connected to the BeagleBone Black. I highly doubt you will be recording with a quality that will take up the entire bandwidth.
Can I record & write concurrently?
The USB protocol is not like SPI or I2C. This protocol is single-endpoint differential signals. The stack specifies an endpoint and the data goes that way. Once the packet is sent over the connection, a new endpoint has to be negotiated whether data is coming back or more is going out to the device. The protocol is fast enough that you will be able to record then write, record then write, without humans being able to tell the difference.