the 2600 is not a sampler, so you are not able to "play" a new wave file via the keyboard. However I control software samplers on a laptop from my 7k with low latency for live multirack playback and accompaniment - that is not built in sampling but the result can be put on SD card for live playback on the 7k using 7k voices to lead and not then needing the laptop.

You are able to play along to a pre-recorded wave file on the SD card, and if you have a SD audio synchro switch in the sequencer menu are able to synchronise the 2600 sequencer to it.

If this is the case one possibility would be to record a wave file of the snare playing the complete song at correct tempo, transfer to SD and then add the rest of the arrangement via the 2600 and/or 2600 sequencer, perhaps using a pattern(s) in composer(s) with the in-built snare removed.

Another possibility is to multitrack on the pc using the wave snare and any other samples you may wish, and play the 2600 audio out for the rest of the arrangement. Then either mix the final song on the pc or mix the song with the part(s) you wish to play live removed, and transfer that to SD.