My wife and I play tenor a lot. She owns a Kung Sinor tenor which has 4 keys and a bent neck. This tenor is little bigger than an alto recorder. By that I mean the knick moves the finger positions upward quite a bit. This makes if easy to get your hands to cover the lower position and the low C keys. It plays both octaves very well. The low C is easy to sound and strong(loud). The keys fall nicely to the hand and are airtight which means the instrument plays all of its notes cleanly and well. I know you are not asking about this instrument but this is a viable choice.