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OASIS - Song Sampling Synthesis

The songs in your iTunes library are a rich source of sound for creating synths, mash ups, and sound effects. OASIS extracts samples from songs in your iTunes library, and from mp3 and wav files that can be imported into the app. A built in pitch detector tags the sounds so they can be loaded into a wavetable synth. The samples can be modified, played, saved, and exported to other apps. OASIS is Core-MIDI compatible and runs on all iOS devices. It is also fully compatible with Audiobus 2.0.

Sound Examples

The following examples were captured on the iOS simulator.

Sound effects generated from the sound track of the 60's TV show "The Invaders." Demonstrates sampling and blending of multiple sounds. Keyboard and portamento effects.

Somewhat more musical effects generated from the theme music of another 60's TV show,"Perry Mason." Resampling and more portamento effects.

Sample from Bach's Invention in A minor. Effect of changing loop length, sample overlap, and envelope. More portamento at the end.

Finally here are samples from "The Invaders" exported via copy/paste to Auto Sampler and played to Holst's "Mars, The Bringer of War."

Operating Instructions

Load Sound Files

Tap "Song" to access the iTunes library on your iOS device. Select a song to import and load into the app. Songs are first converted to a WAV file that is subsequently loaded into the app. A representation of the sound file is displayed in blue/yellow (right/left channels). Tap the play button on the top control bar to start/stop playback.

Tap "Load" to load an MP3 or WAV file from the app's documents directory, which can be accessed from an attached computer via iTunes file sharing or from iCloud. MP3 and WAV files can also be imported via email.

N.B. The song must physically exist of your device. Go to iTunes. If it is in the cloud, you must first download it before it can be loaded into OASIS.

Extract Samples

Tapping the loop button on the top control bar stops playback from advancing causing the sound to loop. Tapping it again resumes playback. The gray rectangle shows the location and length of the loop. Touch the display to move to any position in the sound file. When you do so and playback resumes, notice the rectangle fills from right to left as the loop queue is filled up in the new location.

The dominant pitch of whatever sound is looping is displayed in red on the keyboard. Tapping another key plays the sound at that pitch. OASIS operates in the time-domain so both the tempo and pitch change when you tap different keys. When the left "Once/Loop" switch is off the sound is played once when you tap the key. When it is on the sound loops continuously. The "Length" slider controls the length of the loop from 0 to 3.0 seconds.

Process Samples

When "Blend" is all the way to the right the raw sampled sound is played, either once or in loop mode. Moving the slider to the left blends the sample with previous samples stored in an output buffer. When the slider is all the way to the left it plays only what is in the output buffer. The "Overlap" shifts and adds the sound in output buffer to itself. When the slider is all the way to the right the sample is shifted by 1/2 the length of the loop, when it is all the right to the left there is no shift. Values in between can create interesting rhythmic effects.

Play Samples

The current sampled loop can be played at different pitches using the keyboard. "Attack" and "Release" control the envelope. "Delay" and "Decay" are reverb controls. The "Portamento" slider on the bottom controls the slide from note to note. The sample can also be played from other apps or attached keyboards using MIDI Bridge.

Save and Export Samples

Tap "Save" on the top control bar to save the current sample as a WAV file in the app's documents directory. If the song name is "XXX" and the dominant pitch of the sample is D7, the file name would be "65_XXX.wav". Tap the action button to export the WAV file to other apps via the iOS pasteboard (WAV copy). Auto Sampler supports WAV copy/paste allowing multiple samples from OASIS to be played in a polyphonic environment.

N.B. If the app does not produce any sound when a key is pressed, move the blend control to the right, and/or tap the play button at the top.

Theory of Operation

The top waveform view shows the location of a sample region within the context of the audio data. When a song plays an input loop buffer is filled with data. You can see the buffer fill up when you move the sample region. If we were to simply loop this data there would be an audible click each time the loop cycles from the end back to the beginning (A). For playing the sample once we add a short fade in and fade out (B). In loop mode the sample is shifted and added back to itself create a smooth repeating sound (C).

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