apeSoft has released apeDelay, which they say implements up to 2048 Stereo Spectral Delay lines with Feedback. This is how they describe it...

The algorithm is based on the STFT (i.e. Short Time Fourier Transform) analysis/re-synthesis. The audio signal is converted in abstract 'Frequency Domain', where is manipulated and transformed back again in 'Time Domain'. You can draw three shapes for the Times, Feedbacks and Panning. This is achieved from the multi sliders, who provide a great tool to manage the huge numbers of parameters. You can also benefit of more advanced spectral manipulations like the Spectral Blur, Granulate, Bins Decimator and Freeze.

Features:

• Audiobus and Inter-App Audio support (sender and FX)
• Built In Stereo Sampler with varispeed and scrubbing
• Control Manager LFO for all the Parameters
• Midibus, Virtual Midi and Network: 14 bit NRPN controllers
• File Manager, sharing common audio files via iTunes, Dropbox and AudioCopy
• Snapshots Presets Morphing Pad
• Post Fx: Stereo Delay, Amazing ClassicVerb Low/Hi Shelving and Dynamic Processor

Pricing and Availability:
$5.99 at the app store.

More information:

• Apesoft

• apeMatrix - A Routing App For iOS 11-Jun-18
• Advanced Cross-Synthesis For iOS 24-Dec-14
• A VCS3 For Your iPad 06-Mar-14
• Granular Synth For iPad 11-Oct-12