Review: Castiv Guitar Sidekick for Smartphones

The Castiv Guitar Sidekick is a new device that will allow you to mount your iPhone or similar device to the headstock of your guitar. The Castiv Guitar Sidekick Smartphone Holder for Guitar is available at for $29.99.

The creative uses for the iphone are endless and the Guitar Sidekick will allow hands-free access to all of your music apps while performing or rehearsing. This is especially handy for referencing lyrics, chord changes, or a tuner, or metronome on the fly. I’d love to see someone come up with even more creative and interactive uses for it. Maybe interacting with audience members, taking requests, or even using the camera to document shows or skype with fans.

The Sidekick mounts to the guitar by way of a clamp called a “harpo device” that attaches to the strings behind the headstock. The device supports a swiveling, padded clamp that will easily accommodate the iPhone or other smartphones. Although everything besides the harpo device is made of plastic, the unit seems sturdy and looks like it should hold up to years of use.

Although the Sidekick will fit 99% of all guitars you may want to make sure your axe is a good candidate for the device: On two of my acoustic guitars – both nylon-string classical guitars – there is not enough room to slide the blade of the “harpo” device between the headstock and the strings. So be sure that there is a bit of clearance here on your guitars. You’ll need about 7/64″ of space to use the Guitar Sidekick and I suspect that this may be an issue for most guitars that have a slotted headstock.

On all of my other guitars there is is plenty of room for mounting the harpo device, but depending on the design of the headstock, truss rod covers, etc. you may need to position the clamp a little farther away from the nut in order to make it work. Also, note that the string height behind the nut is not even due to string trees and differences in windings. Once the harpo device is installed this creates increased tension on some of the strings behind the nut, pulling those strings sharp. You will likely need to re-tune once the device is attached. Although the device is clamped onto the strings you should be able to fine-tune your guitar, sort of like tuning with a capo on.

While I’m not sure that I’ll have a regular use for the Guitar Sidekick, I know that there are those that will love the convenience. Check out the video below to see it in action.

6 thoughts on “Review: Castiv Guitar Sidekick for Smartphones

  1. That looks awesome, I’m going to have to get one. I’ve been having real problems tuning in my guitar ever since I got it (I have a poor ear for it…), so this will be great for my iphone tuning app.

  2. This is an amazing invention. Technology seems to continue to blow my mind. I think the ability to reference lyrics will go a long way in helping the educational process. Not to mention the rock stars who go on stage without having clear heads.

    I really like the idea of using it to communicate with the audience. At a concert the musician can talk to the crowd, but the crowd really can’t effectively talk back. A means for doing so would bring a whole new aspect to attending live music events.

  3. This is amazing! I got one as birthday present for my brother and he is so happy about it! He cant live without his guitar a his phone with him.
    After seeing this even if his birthday is like a month away I already ordered it.. it just feel good seeing my brothers smile after seeing it! priceless!

  4. Really fantastic device seems to be helpful for every guitar player.I will order this device.I think nobody has said anything? about using it for easy access to lyrics.

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