The buyer, pending approval by HMV shareholders and regulatory bodies, is a new joint company formed by AEG and CTS Eventim.
Subject to completion of the disposal and the satisfaction of customary conditions precedent, the HMV Group has amended its existing £220m Bank Facility with its existing lenders and extended it to 30 September 2014.
In a statement, HMV said its directors "believe the disposal of HAL will allow management to focus more closely on HMV's strategy for its core business, developing HMV's retail offering with a view to maximising value for all stakeholders...
"The disposal and the amended Bank Facility together represent an important step towards strengthening HMV's capital structure. The proceeds from the disposal will be used to reduce the Group's outstanding debt and for general corporate purposes."
Simon Fox, Chief Executive of HMV Group, said:
"The Hammersmith Apollo is an iconic London venue and it has been a privilege to own it over the last three years. However the sale will enable HMV to extend its bank facilities, strengthen its capital structure and ensure a strong future for the Group. AEG has a great track record in running live venues.
"They and their partner buyer CTS EVENTIM, the leading European ticketing services provider, have impressive and exciting plans for the Hammersmith Apollo and we wish them well."
[Update] HMV paid £46 million to acquire Mama Group in 2010 - misreported in some national press as £64m.
HMV CEO Simon Fox told Music Week last year the company had invested little over £60 million in the subsidiary in total - and that it was looking to recoup that amount and more with the sale of its live music assets.
Mama Group continues to operate the following London venues; HMV Forum (2300), Heaven (1000), The Garage (800), Barfly Camden (450), Jazz Cafe (400) and The Borderline (300), and regionally the Manchester's HMV Ritz (1500), Edinburgh's HMV Picture House (1500) and the HMV Institute in Birmingham (1500).