bs-16i is an sounds expander.
It can play SoundFont and DLS files. You can also import your SoundFont and DLS files from another App, iCloud Drive, Dropbox,...
The Stand Alone version is a 16 tracks sounds expander because of this it comes with a Mixer.
For the Audio Unit you load as many instance of bs-16i as you need.
The other difference is the Midi files player that you will not find in the Audio Unit version.
Excepted that, the 2 synth module are the same.
1/ Output: Volume - Pan- Reverb - Chorus - Delay (Send)
2/ Tune: Coarse - Fine tune - Pitch - Portamento - Mono or Stereo
3/ Eg / Filter: Attack - Decay - Release / Cut-off - Q
4/ Vibrato: Rate - Depth - Delay
In the App in Purchases, you can unlock the High Resolution engine (enables high-quality and low-noise audio outputs by 100% floating point calculations.) and 128 voices of polyphony (64 for the standard version).
To conclude: bs-16i is a Must Have! Yes, because it always useful to have an App like this in our iDevice. On the Web you can find a lot of SoundFont files. A lot of instruments for free... The App is very well done and I like the 2 versions.
A Killer App! A Must Have!
Review by Ed