There has been a trend towards smaller and smaller harmoniums in the kirtan scene, as folks want to have the easiest harmoniums to transport. Two of the smallest are the Shyamdas Backpack and the other really tiny one is the V-Shaped ones frequently seen being used by ISKCON (the "Hare Krishnas") singers. I always try to steer first time buyers toward the larger harmoniums like the Tilak 23 and Signature 23 because they have the best compromise in windchest size, allowing for a transportable instrument that has good full sustain, required to play Western style kirtan like Krishnadas, Jai Uttal etc. The next smallest harmonium that still works very well for Western style harmonium players is the 4B Backpack model. Now everyone knows what I mean when I say Western style harmonium, but I often get blank stares when I mention Hindustani style. Why Hindustani style? Because that style of harmonium playing works well with tiny harmoniums because it uses quick arpeggio style single note runs as opposed to three or four note chords. See the video to understand what I mean by Hindustani style harmonium.