The tenor tagelharpa allows you to create a deeper sound than the traditional. 
Where as the regular altos listed on the site tend to me lighter in sound and more melodical, the tenor tagelharpa gives you the option to create both a deep sound and more melodic riffs than what a deep baritone allows you to. 
 
The tuning can go all the way up from C4-F3-C3 down to F2-C2-F3.

This is a must buy for a tagelharpa player wanting to expand the playability options.