Command line tool to identify audio file specs

On OS X you might just use mdls or mdfind.

$ mdls 01\ Kindred.mp3 
kMDItemAlbum                   = "Kindred EP"
kMDItemAudioBitRate            = 320000
kMDItemAudioChannelCount       = 2
kMDItemAudioSampleRate         = 44100
kMDItemAudioTrackNumber        = 1
kMDItemAuthors                 = (
    Burial
)
kMDItemComment                 = "HDB059"
kMDItemContentCreationDate     = 2012-03-19 21:20:59 +0000
kMDItemContentModificationDate = 2012-06-04 16:07:09 +0000
kMDItemContentType             = "public.mp3"
kMDItemContentTypeTree         = (
    "public.mp3",
    "public.audio",
    "public.audiovisual-content",
    "public.data",
    "public.item",
    "public.content"
)
kMDItemDateAdded               = 2012-04-02 19:49:07 +0000
kMDItemDisplayName             = "01 Kindred.mp3"
kMDItemDurationSeconds         = 686.08
kMDItemFSContentChangeDate     = 2012-06-04 16:07:09 +0000
kMDItemFSCreationDate          = 2012-03-19 21:20:59 +0000
kMDItemFSCreatorCode           = ""
kMDItemFSFinderFlags           = 0
kMDItemFSHasCustomIcon         = 0
kMDItemFSInvisible             = 0
kMDItemFSIsExtensionHidden     = 0
kMDItemFSIsStationery          = 0
kMDItemFSLabel                 = 0
kMDItemFSName                  = "01 Kindred.mp3"
kMDItemFSNodeCount             = 27457838
kMDItemFSOwnerGroupID          = 20
kMDItemFSOwnerUserID           = 501
kMDItemFSSize                  = 27457838
kMDItemFSTypeCode              = ""
kMDItemKind                    = "MP3 audio"
kMDItemLogicalSize             = 27457838
kMDItemMediaTypes              = (
    Sound
)
kMDItemMusicalGenre            = "Dubstep"
kMDItemPhysicalSize            = 27459584
kMDItemRecordingYear           = 2012
kMDItemTitle                   = "Kindred"
kMDItemTotalBitRate            = 320000

mdfind -onlyin ~/Music 'kMDItemFSName==*.mp3&&kMDItemAudioBitRate<=192000'

For easy to parse output, try ffprobe -show_format 2>/dev/null from FFmpeg.

On OS X, you can install it through Homebrew via brew install ffmpeg.

$ ffprobe *.mp3 -show_format 2>/dev/null
[FORMAT]
filename=02. Salvadoro Dali.mp3
nb_streams=2
format_name=mp3
format_long_name=MPEG audio layer 2/3
start_time=0.000000
duration=300.254667
size=7206112
bit_rate=191999
TAG:title=Salvadoro Dali
TAG:artist=Siela
TAG:track=2/10
TAG:album=Dali
TAG:date=2005
TAG:genre=Gothic rock
TAG:replaygain_album_peak=1.188815
TAG:replaygain_track_peak=1.178607
TAG:replaygain_track_gain=-9.00 dB
TAG:replaygain_album_gain=-9.12 dB
TAG:album_artist=Siela
[/FORMAT]

In a script:

find -iname '*.mp3' | while read -r file; do
    bitrate=$(ffprobe "$file" -show_format 2>/dev/null |
              awk -F"=" '$1 == "bit_rate" {print $2}')
    if (( bitrate <= 128000 )); then
        echo "[$bitrate] $file"
    fi
done

EDIT: just found a Linux program

Under Linux, mp3info:

mp3info -p "%Q %L %v %o %r" test.mp3
output:
48000 III 1.000000 joint stereo

I know you want a Linux solution; however, by the way you stated your question, it sounds like a Windows solution is not completely out...

Under Windows, tag.exe will do the job.

Example:

C:\mp3>tag.exe "test.mp3"
Tag - Automatic Tag from filename
Copyright (c) 2002-2003 Case.  Minor additions by Neil Popham, 2004-2007
Version 2.0.52, Compiled 2007-05-04

C:\dl\test.mp3
Format:  MPEG 1 Layer 3, Joint Stereo
Details: 44100 Hz Stereo, 128 kbps, playtime 05:24
Tag:     ID3v2

To just get the bitrate:

C:\mp3>tag.exe "test.mp3" 2>&1 | findstr /i "Details:"
Details: 44100 Hz Stereo, 128 kbps, playtime 05:24