Fight with Mecha-Drago is a battle theme in Mother 3 exclusive to the Mecha-Drago, as the name would imply. It's a sad and nervous song that reflects the brutality forced upon the otherwise peaceful Drago.
You hear this variant in Chapter 3 when the mother Drago starts attacking the Pigmasks and Fassad. It's the same song as Fight With Mecha-Drago , but it's got more drums and is slightly faster. It doesn't use the BPM variable nor has a "heartbeat" soundtrack, so it's not a battle theme.
Fight with Mecha-Drago (unused alternate)
This is an unused "hard" alternate to Fight with Mecha-Drago. The song is the same, except that it's almost completely silent at certain times. During these times, not a single beat plays. At the end, more drums prolong the song. During this period, the player would expect that the rhythm would speed up or slow down, but it remains the same.