This week we make music with Koala Sampler and snap long-exposure photos with Halide’s new app, Spectre Camera. Plus, we keep it together with Keep It Mobile, and way more.

These are the best apps of the week!

Spectre Camera

Capturing the path of light and motion with Spectre Camera.
Ex-Spectre the unexpected.
Photo: Spectre

From the makers of Halide comes Spectre, a brand-new camera app that uses the iPhone’s powerful brain to fake long-exposure photographs.

By day, it will blur moving objects while freezing still subjects — blurred water over a waterfall, for example. By night, it will capture beautiful light trails. Spectre actually takes hundreds of shots during three-, five- or seven-second exposures. Then it examines them to work out what to blur, and what’s moving.

Price: $1.99

Download: Spectre Camera from the App Store (iOS)

Koala Sampler

The attention to detail in Koala Sampler is stunning.
The attention to detail is stunning.
Photo: Cult of Mac

Koala Sampler is the most fun you’ll have this weekend, clothes on or off. It samples any sound through the iPhone (or iPad) mic, then lets you play back the audio.

What sets Koala apart is its amazingly easy “workflow.” You just tap one pad on the grid to record a sample into it. Then you tap that same pad to play the sound.

Songs are equally easy to edit and arrange, and you can add live effects as you perform the song. These effects can also be saved into new trigger pads by resampling them. It’s great stuff, marred only by some absurdly bad spelling and typesetting errors throughout the app.

Price: $2.99

Download: Koala Sampler from the App Store (iOS)

Keep It Mobile

The Keep It app makes keeping it even easier.
Mobile app Keep It makes keeping it even easier.
Photo: Keep It

Keep It is a great shoebox app for everything you want to store, form bookmarks to PDFs to snippets of text. Now it can save webpages as Web Archives as well as PDFs.

Speaking of PDFs, the app now recognizes text inside images and PDFs. If the PDF already contains text, then this makes no difference. But on PDFs without proper embedded text, or on images of handwritten notes, this means you can snap your paper notes into a searchable archive.

Price: Free

Download: Keep It Mobile from the App Store (iOS)

Linea Sketch

Linea now has pressure-sensitive ink, and musical paper.
Linea now has pressure-sensitive ink, and musical paper.
Photo: Icon Factory

A great update to Linea Sketch adds pressure-sensitive strokes. If you press harder with the Apple Pencil, then the line of your current pen or pencil gets thicker. Plus, you can toggle this behavior off right in the individual tool settings.

Also new are stationary backgrounds for musicians — including guitar tabs.

Price: $4.99

Download: Linea Sketch from the App Store (iOS)

MidiWrist

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MidiWrist turns your Apple Watch into a remote control for your musical apps and MIDI hardware. It lets you tap the screen to start recording, use the Digital Crown to turn the virtual knobs on real hardware effects units, and lots more. If you’re a musician and you own an Apple Watch, this is a must-buy.

Price: $4.99

Download: MidiWrist from the App Store (iOS)