Whenever I create a 2nd new midi track and select a different sound patch, like the first track is piano which sounds good. The 2nd track may be horns, I heard the piano & horns when I trigger midi keyboard. When I tap the on screen keyboard I will hear only horns. How can I get my midi keyboard to respond the same?
Chances are you have the MIDI Port patched to both tracks. Ardour works a bit different from others in this regards in that it doesn’t filter per channel on each track, but there is a free plugin for this purpose: x42 MIDI Filter Collection
So assuming you are using different channels on the MIDI keyboard for each patch, then you could filter with the plugins above on the input.
If however you just need to only hear that track temporarily and are not able to filter, just mute/solo the tracks as appropriate.