The Am , Am(7M) and Am7 is basically a step down of the fourth string:

      Am     Am(7M) Am7
e | ----0-------0--------0------- | 
B | ----1-------1--------1------- | 
G | ----2-------1--------0------- | 
D | ----2-------2--------2------- | 
A | ----0-------0--------0------- | 
E | ----x-------x--------x------- | 

The B7 can be played in various ways, I like the sound of this one:

e | ----2--- | 
B | ----0--- | 
G | ----2--- | 
D | ----1--- | 
A | ----2--- | 
E | ----x--- | 


  Am       Am(7M)    Am7      Dm
  A gentle breeze from hushabye mountain

  F      Am         B7      E
  Softly blows o'er lullaby bay

  Am           Am(7M) Am7            Dm
  It fills the sails of boats that are waiting

  F          Am        E      Am
  Waiting to sail your worries away

  
  Dm        B7        E 



  Am       Am(7M) Am7      Dm
  It isn?t far to   hushabye mountain

  F        Am         B7          E
  And your boat waits down by the quay

  Am           Am(7M)  Am7        Dm
  The winds of night so  softly are sighing

  F              Am       E           Am
  Soon they will fly your troubles to sea



  Dm            A       F        G
  So close your eyes on hushabye mountain

  Bb   Dm         B7            E
  Wave goodbye to cares of the day

      Am         Am(7M)  Am7      Dm
  And Watch your boat from hushabye mountain

  F        Am        E       Am
  Sail far away from lullaby bay