WayOutWare's new SynthX ($9.99, introductory price from the iOS App Store) delivers a surprisingly powerful and playable synth to your iPad. SynthX's analog-modeled engine derives from KikAXXE, the company's plug-in emulation of the classic ARP AXXE synth. The two synths can even exchange patches, and the KikAXXE factory banks are included with SynthX. (Some tweaks are necessary when exchanging your custom patches because SynthX has a few added features.)

Play Now, Tweak Later
Let's start with playability. SynthX offers three note-playing surfaces—XY, Grid, and Keys—which occupy the full screen, or the bottom two thirds of the screen when one of the synth's five setup tabs is active. XY mode is much like the 2-dimensional control surface of Jordan Rudess's ubiquitous Morphwiz. Notes within the chosen scale are indicated by vertical lines, but if you choose no scale, the pitch glides continuously as you drag your finger(s) across the screen (see Fig. 1). Even with a scale chosen, you can use the Glide control to make notes slide between scale tones.

FIG. 1: When one of the setup tabs along the top is active, SynthX's note-control surface occupies the bottom two thirds of the screen. XY mode and the Control tab are shown here. Dragging your fingers triggers notes for up to six voices (the current limit on the 1st generation iPad), which are pitch quantized to the chosen scale—C blues scale in this case. The sliders labeled Y-Axis/Pres determine how vertical dragging and MIDI Aftertouch influence volume, filter cutoff, and pulse-width and pitch modulation amounts

Keys mode presents a piano-keyboard graphic and always uses the chromatic scale. In that mode, glide applies when you drag your fingers across the keys, but not when playing individual notes. One of the nicest features of the XY and Keys modes is that you can expand and contract the key range (horizontal zoom) to suit your fingers and playing style.

Grid mode displays 8 rows of 12 notes in a two-dimensional grid. Each square of the Grid triggers a note, and you can set the vertical step size from a semitone to an octave. The horizontal step size is always a semitone. Grid is great for playing parallel patterns of a given interval such as Major Thirds moving up and down in steps of a Perfect Fourth (see Fig. 2).

FIG. 2: In Grid mode, each square of the grid represents a note, starting with C-1 (four octaves below Middle C) in the lower-left corner. The vertical step size is set with the Row buttons at the top. Here the rows are spaced in Perfect Fourths.

In all modes, you can assign the vertical touch-position (as well as incoming MIDI Velocity and Aftertouch) to affect filter cutoff, volume, and modulation amounts as dialed in on the Controls tab. A waveform graphic appears under your fingertip for each note played, and seeing how parameter changes affect those waveforms is actually quite useful for sound-design and modulation settings.

The Synth Within
SynthX's synth engine starts with a noise generator and an oscillator offering sawtooth and pulse waveforms. An LFO, which you can sync to the tempo of incoming MIDI Clock, offers sample-and-hold, square wave, and sine wave modulation sources. You can route those to pitch, pulse-width, and the cutoff frequency of SynthX's resonant lowpass filter. You can route the single ADSR envelope generator to the same destinations as well as to output volume. All settings are made using a row of color-coded sliders above the playing surface (see Fig. 3).

FIG. 3: All synth settings are effected using this row of color-coded sliders. For example, the pink Sine and Square sliders in the Oscillator section control pitch modulation by the LFO, whose label is pink.

The Effects tab reveals distortion, flanger, and delay effects as well as an output limiter (see Fig. 4). All except the limiter have their own XY controller: frequency versus gain for distortion, frequency versus resonance for the flanger, and delay time versus feedback (called regeneration) for the delay. The delay line is modeled after the Echoplex EP2 and has a slider for controlling the input mix of the incoming signal and feedback. You can also use the effects section, with separate settings, to process incoming audio.

FIG. 4: SynthX's distortion, flanger, and delay effects each feature an XY pad for simultaneously controlling two parameters. The Audio and Synth buttons on the left let you create different settings for processing incoming audio and SynthX's synth.

SynthX has a built-in audio recorder to capture its audio as 16-bit, 44.1 kHz WAV files. You can play back recorded files, but looped playback has not yet been implemented. The Audiocopy button uses Sonoma Wireworks' AudioCopy utility to transfer audio to other iPad audio applications, and the number of supported apps is growing rapidly. SynthX also supports iTunes File Sharing. That lets you transfer audio files and patch banks between your iPad and your computer. In my view, that's the easiest and most reliable way to share data with iPad apps, and I wish all developers supported it.

Live from MiPad
SynthX can keep you busy for hours tweaking its sounds and playing its huge collection of presets solo or accompanied by other apps, such as Tiv Studio Beat Vibe, that can stream audio in the background. But you'll eventually want to get it into the act in your studio. The easiest way is to connect the iPad's headphones-out jack to one of the inputs of your audio interface and use that to record your SynthX playing in your DAW. And if you develop some SynthX chops, that may be all you need. The iPad's audio out, although not pristine, is serviceable for many purposes.

If you decide that your iPad is an essential part of your studio gear, you may want to opt for a third-party audio and MIDI interface such as the upcoming Alesis iO Dock. That taps the iPad's I/O via the more reliable 30-pin connector, and it provides standard MIDI, audio, and controller connectivity.

For MIDI both to and from SynthX you have several options. MIDI WiFi is serviceable in both directions. Latency, although improved when SynthX is synced to MIDI Clock, is considerable, but it's easy to compensate after the fact. I had the best results (and the most fun) recording audio played on the SynthX surface, which, after all, is one of its best features. I simultaneously recorded SynthX MIDI output on a separate DAW track for subsequent doubling with other instruments. It was easy to then jog the recorded MIDI to line it up with other parts. You can get much better MIDI performance with a separate interface such as the iOS and CoreMIDI compatible iConnectMIDI.

SynthX is a great buy. For $9.99 you get a different performance perspective, a great sounding portable synth, and easy interconnectivity, should you choose to go that way. I highly recommend it.

Pros: Playing-surface options for a variety of styles. Excellent sound. Easy data and file exchange. Great price.
Cons: No loop playback for recordings. Cannot create custom scales. (Both are planned for a future release.)

Len Sasso is a freelance writer specializing in music technology. For an earful, visit his website, swiftkick.com.