Recording audio that is playing

I sometimes want to record what is playing on my system. Not from the microphone, but what is playing to the headphones or speakers.

I am running Debian  Bullseye. It has a particular configuration of ALSA and PulseAudio that makes it easy.

The command 'pactl list' lists pulse audio devices, including all the sources.

On my system, one of those sources has the name 'alsa_output.pci-0000_00_1f.3-platform-skl_hda_dsp_generic.HiFi__hw_sofhdadsp__sink.monitor' with description 'Monitor of Tiger Lake-LP Smart Sound Technology Audio Controller Speaker + Headphones'. I see this description on the mixer Input Devices tab and it seems to correspond to what is playing on the headphones or speakers.

 arecord -f cd -t wav --max-file-time 3600 --device=pulse:alsa_output.pci-0000_00_1f.3-platform-skl_hda_dsp_generic.HiFi__hw_sofhdadsp__sink.monitor mon.wav

I suspect that the form of device name (`pulse:xxx`) depends on the configuration in /etc/alsa/conf.d/50-pulseaudio.conf:

# Add a specific named PulseAudio pcm and ctl (typically useful for testing)

pcm.pulse {
    @args [ DEVICE ]
    @args.DEVICE {
        type string
        default ""
    }
    type pulse
    device $DEVICE
    hint {
        show {
            @func refer
            name defaults.namehint.basic
        }
        description "PulseAudio Sound Server"
    }
}

ctl.pulse {
    @args [ DEVICE ]
    @args.DEVICE {
        type string
        default ""
    }
    type pulse
    device $DEVICE
}

I think this takes the xxx from 'pulse:xxx' as a parameter and allows access to the PulseAudio device by name.