Pitch stays where it should
Naive slow-down drops the pitch with the tempo and the track becomes unusable for ear training. SheetMuse keeps the pitch fixed, so what you hear at 60% is the same music, slower.
Practice
Slow down any song without changing the pitch
The fastest way to learn a difficult passage is to play it slowly and correctly, then speed it up. SheetMuse slows the recording without dropping the pitch, so a half-speed take still sounds like the song.
Loop the part that is actually hard
Set a loop around the bar you keep dropping and let it run. Most practice time is wasted replaying the parts you can already play on the way to the part you cannot.
Bring the tempo back up as it sticks
Work the speed back towards the original once the passage is reliable. The notation, chords and tab track the tempo throughout, so nothing falls out of sync as you go.
Keep the click honest
The smart metronome follows the song rather than running against it, so a slowed-down take still has something to lock to.