If you use SAVE REC MIX AS WAV TO CARD on a Spider Jam or JM4 Looper, all your tracks are mixed down into a single, mono track. If you subsequently want to edit individual tracks, you are stuck - unless...
There is another way that works very well with Mac GarageBand (but should work with any digital audio editor) and gives the Spider Jam, a multi-tracking facility too.
If you make a recording on the Spider Jam - say Guitar, backing track, Mic or lead, bass, drums, you can save the three tracks as individual WAV files by doing the SAVE REC MIX AS WAV TO CARD thing THREE times with the appropriate PLAYBACK levels turned full up and off eg
Track 1
Song/Drums 100%
Guitar 0%
Mic/Aux/Wav 0%
Track 2
Song/Drums 0%
Guitar 100%
Mic/Aux/Wav 0%
Track 3
Song/Drums 0%
Guitar 0%
Mic/Aux/Wav 100%
Then if you drag these three WAV tracks into separate tracks in GarageBand (or import them as individual tracks), you will have a three track recording in (near) perfect sync. I say 'near' because there might be a miniscule difference in phase, but it's not audible.
You can then edit each track for level, eg, add effects and you can add further tracks by the direct injection method (instrument into USB box). You could do a fade out at the end or, in GarageBand, add one of drum endings on another track and cross fade from the SJ drums to the GB drums.