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README.md

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 # BassMidiAudioUnit
-iOS Audio Unit acting as BassMidi sampler 
+[![GitHub license](https://img.shields.io/github/license/newzik/BassMidiAudioUnit)](https://github.com/newzik/BassMidiAudioUnit/blob/main/LICENSE)
+![alt text](https://img.shields.io/badge/platform-iOS-blueviolet "platform: iOS")
+![alt text](https://img.shields.io/badge/audiounit-AUv3-blue "audiounit: AUv3")
+
+## Background
+Apple's `AVAudioUnitSampler` doesn't support Soundfonts spec 2.01. This is a pity regarding the huge gain of quality brought by the support of "modulators" (more on this topic on sound designer Christian Collins' [blog](https://schristiancollins.wordpress.com/2016/03/02/using-soundfonts-in-2016/)).
+
+That's why at [Newzik](https://www.newzik.com), we decided that instead we should use the great BASSMIDI player built by [Un4seen](https://www.un4seen.com/) which is one of the few library on the market to support SoundFont version 2.01.
+
+## Overview
+The goal of this project is to embed the BASSMIDI library into an AUv3 Audio Unit, so it acts as a Sampler node.
+This way, it makes it possible to insert it into a graph of audio nodes handled by the iOS Audio Engine.
+
+## Basic usage
+The `BassMidiAudioUnit` is enclosed in a xcframework that you should import at the top of your file:
+```swift
+import BassMidiAudioUnitFramework
+```
+
+1. Set the sampling rate of the BASSMIDI library
+```swift
+BassMidiAudioUnit.setup(sampleRate: 44100)
+```
+
+2. Instantiate a BASSMIDI Audio Unit
+```swift
+BassMidiAudioUnit.instantiate(soundFontPath: soundFontPath) { result in
+    guard case .success(let container) = result else { return }
+}
+```
+This will return a container object of type :
+```swift
+public struct BassMidiAudioUnitContainer {
+    public let avAudioUnit: AVAudioUnit
+    public let audioUnit: BassMidiAudioUnit
+}
+```
+
+This way you can attach and connect the `AVAudioUnit` object to the `AVAudioEngine` and set it as the `destinationAudioUnit` of a `AVMusicTrack`:
+
+```swift
+engine.attach(audioUnit)
+let outputHWFormat = engine.outputNode.outputFormat(forBus: 0)
+engine.connect(audioUnit, to: engine.mainMixerNode, format: outputHWFormat)
+track.destinationAudioUnit = audioUnit
+```
+
+## Additional options
+Several additional options can be performed on the audio unit including: transposition, mute and force a program change.
+
+### Transposition
+You can apply a MIDI transposition to the `BassMidiAudioUnit` object by setting a semitone offset value:
+```swift
+bassMidiAudioUnit.transposition = -2 // - 2 semitones
+```
+
+### Muting
+It is also possible to mute the audio output of the `BassMidiAudioUnit`:
+```swift
+bassMidiAudioUnit.isMuted = true
+```
+### Force Program Change
+We also can force a MIDI program change event, in order to select a specific MIDI instrument among the GM Program instrument sound list. 
+(In this case, all subsequent Program Change Events contained in the MIDI sequence will be ignored)
+```swift
+bassMidiAudioUnit.instrument = 22 // Accordion
+```
+
+## About Newzik App 🎼
+The [Newzik app](https://apps.apple.com/app/newzik-lecteur-de-partitions/id966963109) is a wonderful iOS app built for musicians, to create and organize your digital music library. Go check our [website](https://www.newzik.com) if you want to known more about us.
+
+## License 
+BassMidiAudioUnit is distributed under the MIT license. See [LICENSE](LICENSE) for details.