Complex sentence: They were structurally similar to The Ink Spots, especially in their combination of high tenor (Maithe Marshall) and deep bass (Ricks), but their material was more varied, including elements of pop, jazz, R&B and gospel styles.
Split into simpler sentences: They were structurally similar to The Ink Spots, especially in their combination of high tenor (Maithe Marshall) and deep bass (Ricks). However, their material was more varied and included elements of pop, jazz, R&B and gospel styles.