If you have a bit of a budget you can hire a voice over (VO artist) or hire a specialized on hold messages service company. Depending on what your requirements the price may range between $50 – $60 and several hundreds dollars. Sometimes, for a little extra cost, the VO artists can also provide background music.
Cornell's "I'm On Hold" follows some of the industry standards, particularly around frequencies and compression, which is one of the reasons he wrote it with a country-ish melody, wanting something simple but catchy, with only a single instrument and vocals. But in other ways, "I'm On Hold" totally upends the genre by breaking the cardinal rule — that hold music shouldn't call attention to itself.

Our ranges include ‘range one’, ‘range two’, ‘range three’ and ‘range four’ and associated products.
Solo guitar and piano music can also be decent choices provided you avoid songs with extremes of high and low volumes and pitch. Most phone systems come with default tracks that, coincidentally, fall squarely into these categories. If you’d like something a bit different then you can find plenty royalty-free tunes available to purchase online (they’re not all that terrible), but remember you'll need to pay for a PRS license if you want to make use of tracks by a recording artist.