Here are mainly two ways you can record audio coming from computer: the first is using audio recording software and the second relies on an audio cable.

1. How to Record Audio from Computer
Here are mainly two ways you can record audio coming from computer: the
first is using audio recording software and the second relies on an audio
cable. Obviously, the former is more preferable as you don't need to
purchase an extra cable.
So in this post, I am going to show you 3 sound recorders that you can use
to record audio from Windows and Mac computer:
FonePaw Audio Recorder which can record sound from both your computer
and microphone even you don't have a Stereo Mix option on PC;
Windows' integrated Voice Recorder and Stereo Mix;
QuickTime to record audio on Mac computer.
Record Computer/Streaming Audio on Windows 10/8/7
First of all, I would suggest you to try FonePaw Audio Recorder, which can
skip all complicated set-ups and directly record system sound coming from
your computer even the device doesn't offer Stereo Mix option.
It can record sound coming from your computer as well as external
audio from microphone. You may choose to record audio from one of the
sources or record both internal and external sound simultaneously. It also
support schedule recording which can stop a recording automatically so
that you don't need to be around the computer the whole time. After the
recording, the recorded audio can be saved and converted

2. to MP3, WMA, AAC, M4A files.
It is a right tool to record streaming audio from Internet radio stations,
music sites, video platforms (YouTube, Vimeo, etc.), record Skype/VoIP
phone calls or capture any other sound played by your computer.
And since FonePaw Audio Recorder is built into the three-in-one recording
software - FonePaw Screen Recorder, you can use the program to record
computer screen with audio, take screenshots as well.
Step 1 Free download FonePaw Audio Recorder and install it on your
computer.
Step 2 Open the program and you'll find three tools: Audio Recorder,
Video Recorder, Snapshot. To record voice and sound on computer,
click Audio Recorder.
Step 3 Turn on System Sound button if you need to record sound from
computer. And turn on Microphone button when you need to capture your
voice. Toggle on the two buttons if you need to both. You may drag the
slider to control the volume.

3. Step 4 When you are ready, click REC button to start recording. The
recorder will prompt you that you can start or stop recording with hotkeys.
(You can click Change Hotkey to change keyboard shortcuts to the ones
you like).
Step 5 During the recording, you can control the audio volume. To end the
recording, click the rectangle icon.
Tips:

4. You need the recording to end automatically, click the clock icon and enter
the expected duration of the recording. When the time is up, the recorder
will stop and save the recording automatically.
You can decide in what format the audio file should be saved by going to
More Settings> Output > Audio Format.
What Is Stereo Mix & How To Use It to Record Sound from Computer
We all know that Windows has a built-in Voice Recorder, and
disappointingly, the recorder can only record sound from microphone. But
once you enable Stereo Mix option on your PC, you can record the sound on
your computer as it comes out of your speakers.

5. What is this Stereo Mix? Stereo Mix, also called "What you hear" is the
name of output stream after all channels have been mixed. Sound drivers
on your computer probably supports Stereo Mix, however, the option is
usually disabled by default on most Windows (Windows 10/8/7). By
enabling the Stereo Mix option, Voice Recorder can record system sound
on your PC through Stereo Mix instead of microphone.
Now the question is: how can I enable and use Stereo Mix? The following
paragraph will teach you how to use Stereo Mix to record computer audio
without microphone.
Note: On some Windows PC, you may not have this Stereo Mix option at all.
If so, jump to Part 1 to learn how to record computer audio with a
third-party audio recorder without Stereo Mix.
Enable Stereo Mix
Step 1 Right-click audio icon in your system tray and choose Sound from
the list to open Sound panel.
Step 2 Under the Recording tab, right-click Stereo Mix and click Enable.

6. Step 3 To ensure that your audio recorder use Stereo Mix instead of
Microphone to record computer sound, set Stereo Mix as your default
input device.
Tip: If you don't see the Stereo Mix option, the option could be hidden.
Under the recording tab, right-click the blank area and make sure Show
Disabled Device and Show Disconnect Device is checked.
Record Audio from PC
Step 1 Launch Voice Recorder on your PC. You can right-click Windows icon
and use Search to locate the recorder.
Step 2 The Windows Voice Recorder is super simple. Just click the mic
icon in the middle to start recording the audio that is playing on your

7. computer.
Step 3 When the audio you need to record stops, click the blue button
again to end recording.

8. Record Audio from Mac with QuickTime Player
If you are using a Mac computer, you can also record audio from Mac
computer in a simple way: by using QuickTime Player in Mac OS.
Step 1 Launch QuickTime Player on MacBook or iMac.
Step 2 On the top, click File > New Audio Recording, which will open the
audio recording panel.

9. Step 3 On the audio recording panel, you may adjust volume and audio
quality. Click the red Record button to start recording audio on your Mac.
Step 4 Click the Record button again when you feel like stopping the sound
recording.
However, QuickTime Player can only record system audio and streaming
audio on your Mac through microphone. To record the sound as it is
outputting from your Mac's speaker, you can download Soundflower for
Mac to help.
And if you need to record Mac screen with audio, you can
download FonePaw Screen Recorder for Mac.

10. If you have any problem in recording audio on computer, leave your
question below.
Source:
https://www.fonepaw.com/recorder/record-audio-from-computer.html