the cubase 7.5 hangs when closing

almost always. OS Win 7 and Win 10 too. even if only one or two MIDI tracks. what can be done?

Try this one:

http://www.steinberg.net/forums/viewtopic.php?f=226&t=81011

and / or this one:

https://www.steinberg.net/nc/en/support/knowledgebase_new/show_details/kb_show/cubase-crashes-on-quitting-the-application.html?tx_p77sbknowledgebase_pi1[keyword_search]=Crashes%20on%20quitting