 will have its sign changed (negated). It will only
     work if the sample's loop (defined previously) is not too big. The
     speed is based on an internal table.

[15]: Set speed
     Where [15][x][y] means "set speed to x*16+y". Though it is nowhere
     near that simple. Let z = x*16+y. Depending on what values z takes,
     different units of speed are set, there being two: ticks/division
     and beats/minute (though this one is only a label and not strictly
     true). If z=0, then what should tech