KQ Sampei 4+

A sampler synthesizer which sound sets can be changed. It is multi-timbral.
Available Sound Set Formats: Sound Font(sf2), Compressed Sound Font(sf3), Downloadable Sound(DLS)

Supports a part of common MIDI messages (GM, GS, XG, MPE).
Includes a MIDI File Player. It supports Standard MIDI Files and RIFF MIDI Files. It also supports multiple ports and loops.

Supports external storages. DO NOT USE ON-DEMAND LOADING WITH SLOW STORAGES SUCH AS HDD, USB STICKS, SD CARDS.

You can customize sound sets with "Modifiers".
In default, a modifier which adds soft pedal function, and GS Custom Controller mod are being applied. You can select "Original" and disable GS Custom Controller if you want.
Supports Audio Unit v3 and Inter-App Audio. You can use this synth as a plugin for another app such as GarageBand, AUM, Cubasis, etc...

Supports Micro-tuning. Place AnaMark TUN files into Tuning folder.

You can use sound sets as long as the device memory allows.
The actual memory limit seems to be around the half of the hardware RAM.
Not that the limit of Audio Unit is much smaller.
You may be able to load sounds over the memory size if you turn on "Load On Demand" (Streaming load).
In the developer's environment, 4.2 GB of SoundFont could be loaded on an iPhone with 1 GB of memory.

You can play this app with external MIDI devices and Virtual MIDI apps.

URL Scheme: kqsampei://

Includes a sound set, "GeneralUser GS" by S. Christian Collins. I prepared a modifier for this set.
This app developer does not collect any user information other than what is collected by iOS/iPadOS.