Hello Marlon,
SSM stands for source specific multicast.
This means IGMPv3: in SSM a join specifies both the group address G and the source address (actually include or exclude directives)
the ip igmp ssm-map static commands build some IGMPv3 static joins as a reaction to receiving IGMPv2 joins from real users the list is processed if a match is found an IGMPv3 join is created using source 11.3.15.3 and the group address.
see
http://www.cisco.com/en/US/docs/ios/ipmulti/command/reference/imc_03.html#wp1011414
ip igmp access-group has another purpose:
http://www.cisco.com/en/US/docs/ios/ipmulti/command/reference/imc_02.html#wp1011497
by using extended IP access-lists it specifies to what (S,G) pairs users in the lan can make joins.
This is a filter on IGMPv3 joins the other one is a converter the joins statically on the routers and can accomodate hosts that are not IGMPv3 capable.
Be aware that if this behaves like
ip igmp join-group means packets of the (S,G) groups are process switched (it shouldn't be so but it is better to think of)
Hope to help
Giuseppe