If you want to do your own tab or notation, it helps to have loop and slow down software. There are lots of them, and you can find plenty of discussion elsewhere on TB. If you goal is to just learn a riff here and there, any of them work fine. If you want to do a detailed transcription of an entire song, I recommend purchasing Transcribe! by Seventh String. I have no relationship with Seventh String. I just like the software. The key to getting the most out of this program is using the measure markers with automatic beat markers between the measure markers. You edit the measure markers to tell it how many beat per measure (usually 4). Open an MP3 file, hit play and then tap the m key on the 1 of every measure. If you're new at this, look for the backbeat on 2 and 4 to help. Tap s instead of m if the measure is beginning of a new section (e.g., new verse). The measure, section, and automatic beat markers allow the software to calculate tempo. If the time signature is 12/8, consider four beats per measure (e.g., marking dotted quarters). Then save the Transcribe! file. When the file is set up this way, you're ready to go. Highlight a measure at a time for looping. Starting and stopping the loop on a logical place (e.g., measure marker) makes the process lots easier. If a measure marker isn't exactly in the right place, adjust it and the beat markers will adjust automatically. The graphic will help identify beats, and you can use display to adjust the beat markers by sight. You can zoom in or out as necessary. If you're undecided about a particular note, just highlight that particular note. Transcribe! will show you all the notes it "hears" in that loop, but your ear is your best friend. Hunt and peck as necessary to find the right note. It gets easier with practice. For low notes, raise the pitch an octave. If it's old recording fine tune the pitch if your bass tuned to A=440. If you plan to play it in a different key, adjust by half steps. If have trouble setting the measure markers, PM me and I'll send you a file with the measure markers in it.