I read your post twice, I’m not completely clear, but I’ll give some generalizations…
You DO know that midi itself carries no audible content? It’s just information that needs to communicate with & trigger some kind of sound source…like an exterior midi sound module, a midi keyboard with it’s own sounds, or a Virtual Instrument (VSTi).
When you play a midi track in whatever Cubase version you have, or any DAW software for that matter - and of course you have to have some midi information recorded onto that particular midi track (input from your mouse clicks, or from playing a keyboard to record midi)- that track needs to have a sound source assigned to it, a VSTi or sound module as I said above. Typically to do this, next to your chosen/highlighted midi track (which you’ve clicked on with your mouse), to the left section of your Arrange Window (again after a midi track highlighted) you need to select a midi Input & Output there. You can either select a particular source and/or channel, or just select ‘Any’ for the Input, and select whatever you want/need for your Output. Say you want to use a VSTi… go to your VST Instruments list, select a VSTi from it’s drop down menu…either a 3rd party VSTi you’ve installed, or one included with Cubase. After that you’ll have a VSTi available on that midi track you’ve selected/highlighted…say you’ve put Cubase’s own VB-1 bass VSTi in your VST Instruments list, then select that for your midi tracks Output. When you press play you should hear your bass part. Do the same thing for all midi tracks.
Newer versions of Cubase have midi tracks AND instrument tracks. As much as I’ve read the differences, I was never 100% clear, they seem very similar to each other but I use midi tracks…I know others have said the same thing. I do know that instrument tracks cannot go ‘outside’ the DAW to play an external midi sound module, you need to use a midi track for that. But instrument tracks can play the included Cubase VSTi’s. I’m not 100% sure, but I THINK if you select an instrument track, you do not have to select a VSTi in your VST Instruments list 1st, and may be available right from your Instrument track you’ve selected/highlighted(?).
If you’re wanted to use an external sound module, say a Roland JV1010 for example…for a midi track (not an instrument track) for that selected/highlighted MIDI track, select the Roland JV1010 as the output. Unless your M-Audio device has a built-in sound module within it, you would not select that as your output because you won’t hear anything!
Oh, and make sure that you’re Cubase midi channels numbers (1-16) correspond to to your sound sources midi channel numbers. Say, you’re using a midi keyboard/synth, and your Cubase track is midi channel #1…make sure your keyboard is sending/receiving on channel #1.
If you still are not hearing something, be sure your Cubase midi filter is not muting any particular channel…yeah, you can do that…globally, or locally on each channel. By Default, you should be good to go though, unless something had been changed.