‘mano a mano’  - is a tango written by Carlos Gardel and Jose Razzano.  The Lunfardo lyrics, written by Celedonio Flores, describe the tribulations of a man consumed by a love which he hopes will be returned - but this will not happen until the object of his passion falls on hard times.

“Nada debo agradecerte, mano a mano hemos quedado,

no me importa lo que has hecho, lo que haces, ni lo que haras

los favores recibido creo habertelos pagado

y si alguna deuda chica sin querer se me ha olvidado,

en la cuenta del otario si queres se la cargas.”

‘mano a mano’  -  has been recorded by most of the great tango orchestras - there is a great version by Francisco Lomuto.  

‘mano a mano’  - the literal translation is 'hand in hand' or 'hand to hand'

but I much prefer this one:

 ‘we are equal - we are in balance'