Nintendo released the
Data Recorder (HVC-006) for the Famicom.
The Data Recorder is pretty much the typical tape
player. You can use it to listen to music through
your television. The device also have the unique
feature of allowing you to save the data you've
created using Nintendo BASIC, the program that lets
you mess around with sprites and sound on the BASIC
cartridge.

The Data Recorder uses cassette tapes to
record.
The Data Recorder has the standard buttons that a
tape player would have: Play, Stop,
Rewind, Fast Forward, etc. When you push
Eject the top translucent cover to the player
will pop open and allow you to remove the tape. The
Recorder also came with its own exclusive Nintendo
cassette tape.
It's kind of weird when you save data or play the
tape, because the audio sounds a lot like a dial-up
modem. This is because the data is converted to
analog, much like that of a modem. It's just a
standard tape deck, though, so any random tape deck,
or voice recorder for that matter, would be
interchangeable with it.
The Data Recorder is not a common item, and when
sold complete, sells over $50 every time.

The Data Recorder's manual.

This is one of the official Nintendo cassette tapes.