- In 1969 Denny rebuilt the neck on his guitar giving it a low oval shape unlike any guitar on the market at that time.
- In 1970 he replaced the frets using a softer, smaller gauge of fret wire.
- In 1971 he began testing saddles and by 1972 he had created a custom saddle, which he matched with a custom designed nut.
- In 1973 he began lowering string heights and realized how much easier his guitar played when his strings were lower on the fret board.
- In 1974 he tested bracing systems and how they affected sound quality. Soon after he created his own bridge design as he realized he could produce more volume matching his bridge to his custom bracing system.
- In 1975 he tested string gauges and how they not only affected sound quality, but also playability.
- In 1977 he experimented with string spacing and how much faster he could move on the fret board when the strings were properly spaced.
Over a 10-year period Denny had literally rebuilt his guitar from scratch, and the results were astounding. After comparing the biggest brands on the market he realized playability on his guitars was improved approximately 50%.
Not only that, his guitars sounded richer, clearer, and more robust. Over the next decade, Denny would continue testing, constantly revising and upgrading his guitars, and it wasn’t before long that his students began using them.
The results Denny’s students had with these guitars were incredible. Chords and measures that once took weeks to learn were now mastered in days.
Using the Zager teaching method his students were already learning at a rate faster then any other, but when combined with Denny’s custom guitars their learning curve skyrocketed.
Denny realized his students were able to practice 3 to 5 times longer simply because their fingers were no longer in pain.
Denny also discovered from his own playing that he could do things on his guitars that he couldn’t do on other guitars. Riffs and chords that seemed impossible before were now easy. The speed at which he moved on the fret board increased significantly and he became a much better player.
Veteran players were now demanding his guitars because they could play longer, move faster, and enjoy playing more.
Over the next 20 years Denny built and reworked thousands of guitars and honed his skills eventually launching his own brand of “EZ-Play” guitars.